Say each one only drove 1000 miles with it on, that 500,000 miles right there......) of miles on probably well over 1000+ Z32's in engines of varying shape, mileage and power output, that there is absolutely NO proof to show using an UD pulley damages the engine in any way, I think the pulley is just a "cosmetic" NVH damper.
That certainly is a possibility... I have no definitive proof on this issue for either side of the argument. I'm just thinking out loud with the rest of you.