This is standard contract law. With a contract in place, companies are required to adhere to the language of the contract, any any change needs to be negotiated (or the contract needs to expire).
Adding a benefit or removing it without going through a contract causes all kinds of legal liabilities (employees may assume it as a permanent perk). Union leadership also don't typically want perks granted that they didn't negotiate for (why would people "choose" to pay for a union otherwise).
Except there's no contract in place yet, and there's absolutely nothing preventing them from being good people. Except, of course, the vicious demands of capitalism.
Unions are not quite the great deal. They don't add to the value of the company, and their only goal is to redistribute value from company to workers. Which is not a bad deal when all runs smoothly, but come financial stress and unionized companies go under first. Then there's also the question of fairness. Unions are not motivated by merit employee brings, so the leeches end up eating lunch of workers who are productive, causing stagnation. All in all, this is not an ideal arrangement. If I had an option to join a union, I wouldn't
collective bargaining: if you are a fungible asset and the company can replace you and hire somebody else for the same price, no problem, tomorrow, then perhaps a collective bargaining is a good idea. If they can't replace all 10,000 of you for the same price, no problem, tomorrow, but they could on an individual basis, collective bargaining gains leverage and stability.
non-collective bargaining: every individual effectively makes their own deal. if the individual is not fungible, then bargaining en-mass to the lowest common denominator or average contributor will hurt at least some if not all of the individuals. so make your own deal since you are above average and this will be better. plus you avoid the union tax.
so it depends. if you are below average or easily replaceable then UNION is better for you. otherwise, make your own deal on your own merits and avoid the tendency to pull the above-average down to the midling.
unions are machines that thrive on, produce, and require, conformity and therefore must reject individuality.
This is the problem with the adversarial union system.
You can call it a failure of the vicious demands of capitalism, but after decades of watching independent adversary unions destroy whole industries that my family was involved in (aerospace, airlines and steel) - with zero-sum negotiations where one side must loose for the other to win - I've come to the conclusion that the only way to deal with it is to give in and deal with unions and only unions and only in the context of the law.
The unions know that - of course - which is why the Union in Australia is threatening to extend their strike if Apple asks it's local workers there to vote on a proposal, when only 1/4th of the workers are represented by the union.
Alternatively, you could frame the system as the "adversarial employer system" because Apple also chose to be adversarial. Apple could, in good faith, extend the additional benefits to the unionized employees or add their dollar-value worth to their paychecks, contingent on re-negotiating them the next cycle, but instead they choose to hold themselves directly to the minimums they negotiated this cycle and do nothing additional for those employees.
I think this is a pure anti-union move that Apple is marketing via "look, if you just trusted us, and not the evil unions, we could be giving you more!" Where, in reality, the important thing for a union to protect from is the cutting of benefits and lowering of working conditions in those times where it's normal to do so (downturns), because time has proven that those "austerity measures" are rarely reversed by a company when profits rise.
It's even worse than you describe. The store in question has voted to join the union but negotiations on the union contract have yet to begin. So there's not even a "last cycle" here.
A lot of people seem to be missing the fact that adversarial (or adversarial union system) is a term of art and a definition, not simply a talking point (No! It’s not the unions that are adversarial! It’s the evil company! The union is evil - because it’s adversarial!).
As far as companies, unions and good faith go - go read up on some of the less ideal aspects of the adversarial system. Beyond the strike breaking, and violence - It’s relatively common for the zero sum adversarial system to result in outcomes that corporations or unions are willing to literally destroy themselves (over the long run) to win a short term victory. For example, Charlie Bryan demanded to see the books of Eastern Airlines as part of a negotiation, determined that Eastern could not survive without concessions from the unions, and instead chose to maximize their claims and call a strike figuring it was worth getting more for employees, even if it meant the inevitable death of eastern airlines.
You can’t take an adversarial position to your employer, such as joining a union, and then expect your employer to treat you just like a man who isn’t in a union.
There are two sides to any relationship. An employer can choose to begin their relationship with me in a non-adversarial way, accepting that I and my colleagues want to be represented by a union of the group of us and still be decent and try to reward us for the hard work we do, or they can fight it tooth and nail, constantly stick to the "letter of the law" like Apple here (which is just trying to make union and non-union employees feel disconnected from each other and shed negative light on the union), etc. That's why unions also use these tactics to fight back against that (the old "work to rule" or whatever you want to call it).
I expect my employer to treat me as an individual and as a member of a greater collective of humans. Besides, my employer isn't a faceless corporation, it's the management in the chain from my boss up through the CEO, all also humans. Instead, most employers choose to use what power they have over me to make my life harder and make my working time shittier for no reason. Unions didn't just pop out because people felt too comfortable and well-treated at their jobs.
Why joining an union is considered adversarial ? The behaviour of the union can be adversarial but an union is fundamentally just an association of employees.
If an employer considers taking measures to understand and protect your rights to be adverserial, then they're probably screwing you over. A decent employer has nothing to fear from a union. It's like how if someone won't let you read over a contract with your lawyer before signing it, that's a giant red flag that the contract is against your interests.
Perhaps you wouldn't mind sharing examples of these mythical workers who joined a union despite the benevolence of their employer? I suppose those mean heartless laborers left the poor helpless capitalist with no other options.
Worth noting ... there are non-adversarial union systems, cooperatives, worker-councils and even sectorial tripartitism outside of the US legal system way to structure a union.
Adding a benefit or removing it without going through a contract causes all kinds of legal liabilities (employees may assume it as a permanent perk). Union leadership also don't typically want perks granted that they didn't negotiate for (why would people "choose" to pay for a union otherwise).