The problem is that many places want to hire developers and have them deliver as soon as they get a devenv, with zero efforts on training, naturally that only works if the experience is already there.
No, as the article describes, that does not work even if the language/framework experience is already there.
If you're a veteran with Javascript, and Angular, and Node, and MySQL, you will scarcely be able to add something as simple as a "Birthday" field to the user profile pages of your new employer's SPA on your first day or first week on the job. That background will give you an idea of how you would have done that on previous applications, and give a slight speed boost as you try to skim the project for tables and functions that are related to user profiles, but the new application is almost certainly different. If you knew C#, SQLite, and desktop application development instead, or, heck, were fresh out of college with nothing but some toy applications that used Java to write some CSV files, that would scarcely matter, you'd still spend that first day reading through the codebase to understand how user profiles work, and regardless of your experience you're probably merely going to copy-paste and modify the "Occupation" field anyways.
There are a couple minutes of that first day where you're editing a bit of code and it will go slightly faster if you can remember off the top of your head that in Angular, the keyword to parameterize an input[date] field with a maximum value so your users don't accidentally claim to be infants is "ngMax". Or you could go to docs.angularjs.org and look that up in 5 minutes or less, which is a delay, but that doesn't matter much if the other 7 hours and 55 minutes of that first day (and much of the coming weeks and months) will be spent learning the domain-specific details of your business, navigating the project hierarchy, and memorizing the most common table columns and class names.
I think too many hiring managers are unwilling to voice and reason about their subconscious expectation that they're going to hire someone who is a clone of their existing employees. The only developer on the planet with 5 years' experience building a CRM and scheduling tool for landscapers in West Virgina using React/Node/MySQL with database layout and code architecture that matches what you have is named Dave, he's already in the office down the hall, and yes he's behind on v3 because he's swamped with tickets from customers on V2 right now, he needs you to hire someone to help. Just get anyone who's reasonably technically competent and good at problem-solving, and they'll pick it up as has always been done.
The first place I worked as a dev, they had copious amounts of documentation and such an expansive wiki, every time I asked something, the common response was, "fates, it's in the wiki."
I did have quite a bit of onboarding, but after a few weeks, the purpose of handing me off to their documentation was to make me more independent and solve the problems myself
Conversely, I started a new FTE role at a large health care corporation. No training, no onboarding, not even a cursory tour of the network, what source control they use, literally nothing.
The amount of time I wasted learning all of this I'm sure cost the company more money than having a proper onboarding and training program. I pushed my manager and his manager on the importance of onboarding (we were hiring a lot of new devs at the time) but his retort was "it's not in our budget, you just have to learn as you go." Ironically, having spoken up, every time a new dev joined our team, they were pawned off on me to bring them up to speed on everything they needed to know - all the while handling a full load of project work.
Not properly onboarding developers has a huge impact on multiple areas of a business. I was shocked a smaller company knew this, but the larger, entrenched corporation wanted nothing to do with addressing this.
