My opinion is that he's BSing.
Chuck Rainey once told me that the only other person to play on Beatles records was Billy Preston. There is a picture of what appears to be a young Purdie, however, sitting next to Ringo on an airplane among the pictures inside "The White Album."
It is possible simply because so many instrumental tracks are ghosted by great studio players. I know for a fact that the late Yogi Horton played a number of Charlie Watts' parts in the eighties, up until his untimely death. The first time I saw Purdie work he set up a little sandwich sign in front of the bass drum that said "BP, that little ole hitmaker....me!"
After the date was over he flipped the sign to read "DID IT AGAIN!"
I have a professional relationship with him that often has seemed personal, as he is a consumate studio musician politician. He has a king sized ego (deserved, I suppose) and often given to a bit of elaboration, from my experience.
When it comes to playing the drums he is among the best, even now, at close to 70.