> By the time you're being performance managed, your boss, their boss, their boss, etc. know about it, and the higher you go in the chain the more you're just a line in a spreadsheet

This is so true.

I've never been "performance managed", but if I were to be, I'd immediately start looking for another job because of what you're describing. Even if I wasn't eventually fired, I know that black mark will color everyone's perception of me from then on.