Just venturing a guess--I'd say it is part of the Dwight effect. When they initiate a post up with him the first thing they do is clear out the wing player from that side to prevent them from helping on D. This means that if Dwight passes back out it goes up top and it is less likely to find its way to the corner.
I would also add that we are using our drive and kick game less which I think led to many corner threes last year.
agree. When you throw the ball into the post (you hope the big man posts with a 45% angle), the entry passer can't clock-down/relocate to the corner because that would essentially allow the defender to collapse down, clog space, and enable an easy double on the block; therefore, that's why you see a lot of rockets' players dump it down, and clock up to the top of the key, or cut through to create more space for dwight to work.