I have an '05 Audi A4, 1.8, fwd, 35k miles. From the beginning, brake dust formed on the rear wheels at twice the rate of the front. At 32k miles, the rear pads had to be replaced, but the dealerwould not acknlowledge a problem and gave the rotors a clean bill of health. The rotors have noticable wear when compared to the front rotors.
The dealer is well-coached in cyclical conversation and I am not able to get any useful information about possible brake-drag or caliper malfunction.
I have driven many vehicles and have never had the rear pads wear out so far ahead of the front pads.
The parking brake is seldom used and driving habits are gentle and unremarkable.

Is this an "Audi" thing or do I have a real problem?

 

On my 2.7T the rear brakes were down to metal at 80k km/50k .
The front were replaced at 60k km /38k.

It’s not common to have the rear brakes replaced before the fronts.
Do you have observations how the pads were worn?
Left and right; inner and outer?
Were they all the same worndown condition or some more the others?
Do you have solid rotors? Were the rear rotors machined?
It’s against the industry code to put pads w/o machining the rotors.
You might want to see other dealer before your warranty expires as the calipers are expensive.
Some dealers have policies for intensive replacements under warranties, some are quite scroodgy.
There is a valve (formerly “proportional”) that functions as a splitter of the braking pressure between front and rear brakes. The rear gets less.
In your case the symptoms are as the rear gets more braking power.

Would you get blocked wheels or the ABS is able to prevent it, hard to say.