Marvel takes it as a point of pride that they've never had to do any sweeping retcons like 'Crisis' to clear up their continuity - however, that doesn't mean their continuity is clear; far from it. They have an unwelcome tendency to say 'no, it didn't happen that way - it happened THIS way' when a particular story is inconvenient for their purposes - who cares if it throws everything else off? At least they have an excuse to show Wolverine fighting someone.