Fair enough but would argue that Crosby in 16/17 was a return to form after two seasons (one really) that were outliers. He was clearly affected in 14/15 by illness after looking like he was going win another easy Art Ross.
By your thinking, would still argue that 17/18 makes more sense if we limit the discussion strictly to regular season offensive production but even then, how much do we penalize Crosby for having a two Cup hangover.
I agree there were good reasons to believe that Crosby's previous 2 were outliers (the success after Sullivan was hired being a big one as well), and believing that his more polished game and experience made him the player you would want in the playoffs. But I think it was also fair to wonder if the other two season were signs that he couldn't be expected to stay at that top level all the time, and so McDavid would be the better bet over a full season. Often part of aging isn't so much a decrease in that top level but in being able to bring that every night, and declines aren't usually a steady slope but some some spikes on the way down, which we've actually seen with a weaker '18 followed by another strong '19. I think people were pretty split on who was going to be better coming into the '18 season, which was fair, and McDavid established himself during it.