> Another reason I really don't trust that to be true is that I've never seen a good way to measure who is a top performer and who is not.

I can work at a new place for a week and know who the top performers are. Their names are all over the commits, and whenever you ask someone a question, you get funneled to the top performers.

Then you talk to them. If they're open and engaging, and don't seem like they got their status just by being around forever, they're almost certainly a top performer.