Edit:
Ok, so maybe I was dumb......
It seems the F1 (help) came in handy today after I typed the previous post.
"This is used to limit torque output during shifts. This helps prevent wear on the clutches and also reduces shift flaring."
If I am reading this right, then there
IS something going on during the engine torque reduction that has to do with transmission operation. What exactly though? I was thinking "defuel during shifts" as is the case with the Duramax/Allison because setting the torque reduction values around 70% for a low load 1-2 shift creates a dip in the RPM only during the shift and then it recovers and begins accelerating again.
So many questions.....are you sick of me yet?