It's a perfect example of the non-existent normative person... which is a consistent issue throughout stats, not just baseball stats. Just because the average male is 5'10.5" (or whatever it is), that is not a good reason to expect a random guy to be 5'10.5". Same basic idea...And his largest sample shows him to be a .740 OPS player.
Not saying that looking at that is irrational... just saying you gotta realize he's never been very close to hitting .740, not even once....