In theory that would be good. The issue is that a lot of managers don't like dealing with problems. If somebody is doing badly and maybe should be fired (which is what a PIP is supposed to indicate) you don't want a manager just passing the buck to some unsuspecting team.

Ultimately, I think you're right. It's impossible to build a bureaucratic pachinko machine that will make the correct personnel decisions. You really need line managers dedicated to coaching staff, and higher-level managers coaching line managers. One-size-fits-all rules are not the optimal solution. But bad management is endemic in so many organizations that I'm sure these abuses go on all the time.