I have had this same issue since the truck was brand new. I first noticed it with an empty truck on a long mountain pull in West Virginia. It seemed engine control calibration related. After pulling some heavy trailers (also with surging) is seems a little better. I think GM spent absolutely no seat time in calibration with this power train and heavy loads. It never does it with an empty truck where I live which is 6 miles from the GM proving grounds.
I have the same issue on my 2022 L8T. I noticed it in West Virginia with an empty truck. It feels like it’s dropping quite a bit of power and then returning it suddenly. It’s not a torque converter shudder, I’ve had that on a car before. I haven’t complained yet but I am planning to when I get the rest of my deleted options installed.(chip shortage)