How is that related? That can already happen if a company decide to have this approach. See also companies that have PIP targets.
Presumably companies have a good idea of employees' skill sets when they hire them, or they terminate the contract by the end of the probation period, so they can also plan for this necessary learning.
It’s related in the sense that if your set of skills becomes irrelevant, you get replaced. Want to keep your job then learn the things reqiured to keep your job.
Say you’re a truck driver. You have your license to drive a truck and every year you need to do your vision test to keep your license. If one day you have to buy glasses, well, tough luck - they come out of your pocket. Otherwise you can’t drive and your employer cannot put you on a truck.
Of course there are always people who are trying to one-up or push ahead up the career-advancement ladder... but I've never ever seen a better candidate appear and challenge someone's position directly. If someone started a new job and starting calling someone out for not doing their job as well, they'd be fired pretty quickly. That's just outright hostile behavior.
Granted I've always worked outside of the valley, I guess FAANG positions can be more hostile.
Presumably companies have a good idea of employees' skill sets when they hire them, or they terminate the contract by the end of the probation period, so they can also plan for this necessary learning.