This is from the developer's chat in November 2007:
Are a player's height and weight at all factored into the game or are they strictly cosmetic for the roster sheet? (mulder613 - Hall of Famer - 2:00 PM)
Cosmetic. Height and weight are (for the most part) reflected in their ratings but they can have impact, e.g. if my PF grows 2 inches from season to season, you'll most likely see corresponding increases to rebounding and shot blocking.
In regards to athleticism, does finishing around the basket translate to dunking? Does height matter at all when it comes to dunking or is it just athleticism? (njh144 - Hall of Famer - 2:02 PM)
Yes, both dunking and just finishing in traffic.