Granted. I really see two different issues here. Shore shouldn't have been credited with a perfect game in the first place since, even though he individually was perfect, the team wasn't (team pitching statistics were charged with one walk, and a no-hitter or perfect game is a team effort regardless of whether there was one or more than one pitcher involved). Given that he was credited with a perfect game under the rules that existed at the time, though, I don't think it should be taken away when the rules are changed. New rules should apply to the future, not retroactively to the past.