You're probably more right than you think.I get something similar every now and again. It usually happens if I let off the gas seemingly at a specific time and then try to accelerate again. I think the computer may be on the cusp of deciding to shift up.
I could be wrong though as I'm in the same boat as you as I dont know much about engines.
These engines are designed to be fuel savers, and therefore it might get confused here and there when you go WOT out of nowhere.
Honestly, I always make it a point to be in tiptronic mode before going WOT because I know for a fact that it's going to give me power when I need it (That, and I desperately miss my MTX )