Hiring is tough and you waste a lot of time onboarding people and getting them to a productive state, firing them just to save some stock after 50 weeks seems a bad idea, not to mention the morale implications.
A good example of this is the This American Life story on NUMMI: https://www.thisamericanlife.org/561/nummi-2015
Toyota took one of GM's worst plants and turned it into one of its best by treating workers with respect. Hearing the workers talk about the transformation stunned me.
* not trusting your team to do their work and by extension questioning whether they are working "hard enough" (or dreaming of ways to extract more blood from stones)
* some flavor of impostor syndrome, needing to prove your value by making sweeping changes to the team process even if inheriting a successful team
* not having either the back bone or clout to question status quo, including demoralizing cultural habits such as stack ranking
There is a reason the majority of employers (including managers) are generally bad and the good ones are few and far between - it's human nature.
I'm reminded of Microsoft Japan piloting a 4 day work week and announcing in 2019 that the trial ended up increasing productivity by 40%. They ended up not making the change permanent. One small company in New Zealand - Perpetual Guardian - did the same trial in 2018 and saw the same effect, they made it permanent.
Most companies operate like Microsoft.
Broken systems product broken systems.
Not sure if that's really their concern here. Companies don't just ditch reasonably well performing employees because they want to avoid compensating them. That would already mean that each time RSUs vest the company would have an incentive to fire.