The rear may do most of the pushing but the fronts do 100% of the steering, braking, supporting most of the weight and some of the power. If an AWD can't spin the tires and mine can't, the rears will not wear faster.

 

On my FWD cars, fronts wore faster, vice-versa for RWD. I guess I’m not an aggressive enough driver to make braking impact wear on the fronts substantially.

And I guess with the GS and the Infiniti G35 I had last, the fronts get so dirty with brake dust that I deliberately try not to brake aggressively, otherwise I’d be out there cleaning the front wheels every day.

I clean my front wheels once or twice a week between washes.

 

This has always been my experience as well - that's why I was thinking the rear would wear faster given the rear gets a greater amount of the power distribution (I'm assuming most of the time except when necessary due to snow, etc...). On the Subaru with it's symmetrical AWD all of the tires have always stayed very close in terms of tread depth even when there's been delays in getting them rotated.