You raise an interesting point with manual transmissions. However AWD is not like 4-Wheel Drive, in which the wheels are working in tandem and slightly against each other (it’s why you can’t drive at 70 in 4WD mode).
AWD really only kicks in when there’s a hint of slip, to my knowledge, in acceleration. Downshifts that cause slippage might be able to use AWD, but for sure ABS/Stability/Traction control would.
Consumer Reports appears to think AWD engine breaking was not worth mentioning. To be fair, it’s not a standard way of assessing a car for winter driving.
Interesting thought, though, and I’d like to know more.