I don't see that as part of the problem. Though we haven't heard from the OP as to whether or not this is just rubbing noise they hear while moving the bike around in the quietness of their house or garage, or if this is in fact noise while actually riding the bike.

As I said, on cars, there is nothing to pull the pad away from the disc. It's just that the piston is not putting any pressure on the pads anymore. So a microscopic distance is okay to prevent friction that is actually causing one to work harder propelling their bike.