Although I've heard that rumor before too, it's my opinion that the real cause of X40 pre-mature rear brake pad wear is due to the fact that the rear pads simply fit too tight and thus easily rust, causing them to stick rather than move freely with brakes released. A similar problem also can occur in 850 and X70 rear brakes with a little rust, the pads rust in place.
You'll never see it in writing as my method's "unscientic" but we grind some material from the new pads edges so that they fit better (looser) in the rear calipers. We then use anti-sieze on those sliding surfaces. To date we're not seeing problems with those cars and I believe their rear pads are now lasting longer than the previous 15K miles.
I havent yet de-adjusted any X40 emergency brake cables for pre-mature rear.