I think you're being overly restrictive in your interpretation. It doesn't necessarily have to be hardware disabled to not have commands issued to it. It just has a little more power overhead, which is absolutely fine given it's in a reduced performance mode with much lower clocks.
Right in the white paper is in an initialization signal sent to the wave controller for a WGP. It's not unreasonable to think that controller could be left idle and not fetch commands.
Think about it logically. Does it make sense to architect a design around a legacy support mode, including changing baseline mode performance and cost, instead of adding a simple enable signal to an instruction unit?
The Xbox One X's 44 CUs aren't a clean multiple of 12, and it supports S games all the same.
This.
well Sony even being seen as the underdog when they outsold 360 globally, suggests a US-centric world view in the reporting
They only outsold the 360 after the gen was over. Or at least it only came to light by then.