I had this happen in the old engine as well...a shooting guard with a Reb rating of 6 pulled in 12 boards in one game late in the non-conf schedule...he'd had 16 total up to that point in the season, counting his two exhibition games, and never got more than four in a game after that.
Mentally, I rationalized it as he was faster/more athletic than his counterpart and he was winning balls via hustle rather than rebounding technique. *shrugs*
I'd just chalk it up as a quirky game unless it starts popping up with regularity.