I suspect the main justification for the change around manual/auto, was the fact suitable manual LGV and PSVs were getting rare.
I sat my cat C over 10 years ago, just after C+E could be done using a tractor unit and trailer, and the company I sat it with had just spent a couple months finding a suitable newish tractor unit for training, as there just wasn't any available. Since gearboxes like the ZF AS-Tronic came out in the late 90s, pretty much all tractor units have been automatics. PSVs were largely automatics before then, yet everybody sitting a test still wanted a manual license, despite that they were never likely to drive a manual LGV/PSV.
However 7.5ts are still largely manuals, as there really isn't any benefit of autos at that size.
Sub 7500kg are starting to be mainly manual. Ambulances have already gone that way for years & they are a big C1 sector.
For BE towing most 4x4, big, executive type cars are all auto. Add in elec & hybrid & the auto market is growing fast.