People who want to leave and have options, will consider those options either way. There is no way for meta to force them to stay. Even if meta announced layoffs with all the list of names, following months many who want will leave. Pretty much every layoff is followed by people leaving voluntary. Some over bad feelings of what happened, some because their friends are away so why not and some dont like new position. But they will be leaving.

> it's always the less competent employees that hold on for dear life and stay.

Meh. People stay for many reasons. It is not always "not having options". It is fairly often "I actually want to stay despite layoff". And again, there is no way to force people to stay. Confident people will be leaving either way.