Technically it's still banks of 8, but you can redefine what inputs are in that bank. I could make a bank that pulls Local 1&2, AES50-A 12&3, Card 1, 7, and 26, and Talkback 1. When I flip fader banks those 8 will all move together, but I can define them to be any 8 inputs.Yes, custom layers is wonderful.
It's very apparent because any fader can have any function. So I can have inputs mixed with DCAs and output faders, all on the same layer, right next to each other. This is really helpful because I personally hate controlling the reverb return and love that I can assign the reverb send to a DCA and put it right next to all my vocals.
My recollection on the X32 is you can only adjust layer functions in banks of 8.
Your example of mixing in DCA's is valid- the User Banks only work for inputs, and there's not a way to do the same with outputs.