You don't have to share personal details that would compromise your identity but after being placed on one myself, and deciding to quit soon after; I always felt it was unwarranted, unexpected, and retaliatory (but not enough to form a fuss over it and pursue any type of action after I left). After dedicating so much time (including lots of overtime and weekends; and going above and beyond with above average annual reviews), I always felt it was never about performance but something else but hard to prove. Hence why PIPs are always the tool for companies to use to get rid of someone.
Anyone else care to share if you feel comfy?