This possibly the worst way to "trim", because it's not the low performers they will be trimming off, it's the ones who are bad at politics or networking will be let go.
However, there are still people who are bad at their job and are not good enough at politics/networking to survive a layoff/firing. And there are a set of people who are not liked by an incompetent manager and will also probably be managed out who do not deserve it and are good workers.
So you lose some at the top, some at the bottom, and some in the middle. The issue for Meta, will these actions be able to get rid of enough of the unproductive people to be worth it?
The other issue: morale always goes down after these kinds of things. So I think there is a good chance that overall productivity will go down as people do enough not to be marked for firing, but are not motivated to go above and beyond.
I personally think that Mark Zucherberg doesn't have the charisma to deliver this message in a way that doesn't actually cause harm to the company. But time will tell.
More than likely Facebook (sorry, Meta) will probably do it by team and trim underperforming departments. A low performer in an important department is probably more likely to stick around than a high performer in a money pit.
It's probably one of the more rigorous systems in the tech industry that at least avoids this kind of bias, though there are certainly ways it can be gamed.
Objectively evaluating performance of somebody who is smarter than you is incredibly hard, and sliding into using "s/he is a nice person" metric instead, is an easy way to avoid that hard work.
Most corporate places I have worked at have generally done a good job giving me reliable performance reports (I've never been on a PIP but I hear it's incredibly common). Like, no one should ever be blindsided that they are underperforming.
It's still unfair, but doesn't disproportionately affect a specific group as much.
https://en.wikipedia.org/wiki/Decimation_(punishment)
Romans knew what they are doing!