Hmmm. From this, some folks might say I drive like a pussy...
My 2007 325d needed front pads at 88k miles to pass an mot. The rears were still seviceable!
I sold the car just after, so not sure how many miles the rears finally managed.
My 2011 325d (around 19k miles), is showing something like yours on the information page and I don't believe it for a second.
It's a manual and I almost always use engine braking when slowing down.
(That's supposed to be some sort of defence on the 88k miles)....
If the rears need changing that soon, they must be made of f'ing chocolate!