I agree there's some contact but the rotor shouldn't be hot. You could try an experiment and ride 10 - 20 miles in your "normal" riding position/style using only your front brake to stop.... if the rear disk is hot perhaps you have a stuck caliper.
On my way to work this morning, when it was only 84F, I forgot and used the back brake. On my way home, when it was 105F, I remembered, and rode home (about 14 miles) with only the front brake. WHen I got home, the front rotors were too hot to touch, and the back rotors were hot, but no where near as hot as the front...and I would expect them to be warm from the ambient emperature, the exhaust, the engine, etc.
With the lever lower, I did decide that I don't ride the brake without knowing it, my foot position is fine.
This was good practise, since it reminded me how little the back brakes really work, and also just as a reminder to stay off the back brake. When I rented the BMW R1150RT in June, it had linked brakes, which means you have no choice but to brake in the rear, regardless of whether you want to or not.