This. I've been "in the loop" on several people getting PIPs. Two were 100% a pretext for firing. One of those two was fired less than a week after going on the PIP, despite it being a six week plan. I thought that was especially shitty as it didn't give the person sufficient time to line up other work.

The third instance was "we wanna fire this person but if we see improvement then they can stay". This person stayed for almost a year.

In all cases the PIP was to create a paper trail to support an argument of firing for legal cause in a potential lawsuit.