That's my question ultimately. What the reporting sounds like is if you work from outside SV, even if fully remote, you are subject to an unagreed-upon wage reduction. Simply because a pandemic has forced employers to bend doesn't mean employees are forced to do so.
That said, I recognize the difference between ideal and practical reality of the situation. Employees at tech firms typically have little individual negotiation power, but an employment agreement typically can't be amended at the whim of one party. I'm not saying you see it that way, just an outside observer here.
There are no initial employee agreement terms being amended and I'm a bit confused on how it could be interpreted that way. The initial agreement still holds, but FB is extending an additional option that was not offered originally for the employee to change their location to work fully remote, at which point he/she would be subject to the wage multiplier based on market.
That said, I recognize the difference between ideal and practical reality of the situation. Employees at tech firms typically have little individual negotiation power, but an employment agreement typically can't be amended at the whim of one party. I'm not saying you see it that way, just an outside observer here.