I honestly think that if one were to go back and review the tape, Duncan's BPG number would go up by about one. I think the culprit is the subtlety of those blocks he gets where he nonchalantly pins the ball against the backboard/rim before he grabs it a split second later. But yeah, I agree that he seems to get shortchanged at home, which is inexcusable.
Digging a little deeper:
Blocks Per Game
2.14 home
2.81 road
That's a >30% increase on the road. That's a drastic difference; 2.81 would be third in the NBA and could make TD the leading candidate for DPOY.
The home statistician needs some film study to learn what a block is or needs to be fired, tbh.