It's a weird one.
Since he definitely played on loads of records with James Brown, Aretha Franklin, Louis Armstrong, Dizzy Gillespie, Steely Dan, Peter, Paul & Mary, John Lee Hooker, King Curtis, Gil Scott Heron, Roberta Flack, Quincy Jones, Roy Ayres, the list goes on and on, he has no need to boost his fame, so it's a strange claim to make. But he made it on a number of occasions, even though people have looked at the timelines of who was where doing what when and found it was only possible for him to have been on 2 Beatles songs at most, even if what he claimed had any truth.