There's an element of hindsight in it. After the Beatles were a success Johnny Hamp had said that he'd seen the Beatles in Hamburg and thought they'd become a major success. Henri Henroid who was booking groups into Hamburg for Don Arden at the time said he was with Johnny when he saw the Beatles and Johnny said they were a scruffy talentless bunch. George Martin at the time said he was surprised that Pete Best was sacked because he was an asset to the group. He only wanted to use a session drummer because the drumming needed for recording was different from that for stage performances. He also, together with Ron Richards and Paul McCartney didn't think much of Ringo on his first session, so they hired a session drummer then. Yet decades later, George then says that Pete wasn't a good enough drummer - I think that is a result of all the books that have appeared since. There are numerous other examples.