Do pads really get pulled away from the disc on bikes with disc brakes?
I haven't changed mine yet so I don't know. But on a car, at least the ones I've worked on, the brake pads aren't physically connected to the pistons that push them into the rotor. They rely on the ever so slight wobble in the rotor to push them away from them when pressure is relaxed on the piston.
However too much wobble of the rotor is a bad thing. You'll feel it in the brakes on a car. On the other hand, if the rotor amazingly has absolutely no wobble, warpage or run out, it's still not an issue because there is no pressure on the pads.
I'd think bikes would be similar. So if you are just talking about the scrubbing you might hear when moving the bike around, that shouldn't be an issue. It's only if you hear that scrubbing constantly while riding that it's an issue IMO.
But for times you are off the bike just moving it around it doesn't take much rub to make a lot of noise.