Is Google using PIPs to cut headcount, or is that just paranoia?

Partly true. PIPs existed before the layoffs, but the bar for who gets one dropped a lot in 2023 and 2024. People who'd have been "fine" before are getting them now for not being impactful enough, and from what I've seen most don't make it through. Not purely a headcount tool, but it gets used that way when it's convenient.