I had a guy pull the "you never said anything about this before!" act once when I initiated a PIP for him. I had my notes ready and asked him if he remembered our conversations on February 4th, 11th, 18th, (dates are for illustration only) etc. for three months, weekly meetings REQUESTED BY HIM, discussing his lack of performance. He, of course, did not, including the one two days before the PIP meeting. We then had a further two months of weekly meetings while he failed to progress even a little. No effort from him at all. What an unnecessary beating for both of us.
Before him, I thought that having to fire someone signified that I had failed to provide enough training, motivation, leadership, or tools for the folks that I fired. He made me realize that someone else's failure or refusal to perform was on them, not me. Sometimes you hire the wrong one, and you have to cut bait to make a place for someone better.