the thing to consider is the type of human being that can play the various positions and the different requirements.
the higher the requirements for athelticism, the less likely you see the bigger guys.
it's not that it takes less to play 1b, well it does, atheletically. so the big, slow, yet very coordinated guys can play there. "slow" for a mlb player, not slow for an average person
you can have a fat pitcher that is a hall of famer, and being fat had no affect on that - upto a point.
some positions will simply have a greater weight on defense than others, and that will impact which body type and atheleticism etc you will likely see there. always exceptions. this is more about quantity and reduced likelihood of an a-rod type guy playing SS, which he could have for a longer time.
the gist is often known. what the data mining will give you is is greater resolution, and sometimes correct long-standing beliefs that happen to be erroneous. some things the stats tell us now will be corrected later, too.
a whole bunch of stuff is relative to how the game is currently played, too. A higher BA league will shift some weights around etc. if there's a huge power drought, the increases the relative weight of other things like baserunning and stealing compared to what some 10-year baseline might say.