That IRC rule also applies to furnaces. As far as I can determine, rceptacles are to be mounted at the same height as those withing the dwelling, they just have to be GFCI. But is does raise some interesting questions, since people store all kinds of combustibles in their garages.
There’s been several discussions about this topic over at inspectionnews.com over the years. While I don’t remember the exact terminology used, it always seems to come down to the difference between a “permanently installed appliance” and an “attended appliance.” Attended appliances such as dryers and washers are not required to be raised.
I had one inspection a couple of years ago where the dryer was raised 18 inches but the water heater was not. Well, at least the intent was there.
Russel is correct. This was on this board a couple months ago. I think Jeff Pope also said the same as Russel…
Jeff and RR agreeing on something!! Now that’s news. 
Jeff and I agree on a lot. Concrete cracks and swimming pools, however, are not included. I keep referring business to him because I just don’t want to drive anywhere near La-La-Land.