I'm looking to buy a new rotor (160mm) for Vaya. It has an XT Deore groupset. In looking at the Shimano spec page for Icetech SM-RT81, it says "for rear only in MTB usage." I'm curious why that is. See this page, the in Remarks section:
SHIMANO's DEORE XT SM-RT81 compact and lightweight disc brake rotors feature rapid heat dissipation thanks to a deeper disc area and ICE TECHNOLOGIES heat management system. Installing and removing the rotors is quick and easy thanks to SHIMANO's CENTER LOCK design.