Do 4L-80Es whine in first gear?

[Pinger]

Mass Air Flow sensor did all of that?

Yep.
It's the only thing that's changed that has any effect on the transmission. The hard shifts vanished immediately but these last couple of days is the first I've been out for decent length journeys and the difference in shifting as I've described is so noticeable - and transformative.

When I see constant questions from people asking if they should change to a carb because they are having trouble with the injection kit and the advice is invariably 'fix what you have', I'd add losing the MAF as another reason to do that.
I'm running an LPG system that doesn't even use the MAF for its operation but still reinstating it has transformed the truck.

 

[L31MaxExpress]

DTCs P0101, P0102, or P0103 make the blackbox default to maximum line pressure.

 

[Pinger]

DTCs P0101, P0102, or P0103 make the blackbox default to maximum line pressure.

The hard shifts had been bugging me (and the over zealous downshifting and a reluctance to up shift) and I changed the fluid as a first step to cure the hard shifts - just in case it was the cause - and because it's a good thing to do anyway.
I was aware that the MAF inputted transmission behaviour but my suspicion was that the LPG mixer in the inlet tract was screwing things up. Only when I found that the fuse for the MAF circuit was missing did it all fall into place. That fuse also serves the O2 sensor heaters and I can see on my AFR gauge that they work better also. Why (and by whom) the fuse was removed remains a mystery.