The question is: is that true as i have never heard that before.
I'd be very cautious about using a butcher or a store that doesn't clean out their product well in advance of visible mold growth.
Most butchers are very conscientious about removing bone dust... if for no other reason than to be putting a good looking product on display.
I was going to say... does it really matter where the mold comes from? I know to me it doesn't. I don't want to be hearing excuses as to why the meat in display is moldy!!