Because there are tuning limitations with the 6.7 that demand a defuel at 3200rpm.
In fact. I have no problem with you as an individual. But your claims, your numbers, and your 6.7 experience without any actual graphs, videos, or actual proof is why everyone on this forum jumps on your back. Prove me wrong. Post a video of your tach pegging 4400 before a shift and I will admit that I am wrong. We don't even know for sure that you even drive a 6.7..
Again, I have no problem with you here, but I am trying to figure out where you get all of this data when everyone else who has documented results is seeing something different than you.