The short answer: Yes, it's a problem.
It's a constant problem at the monorail resorts, and to a lesser extent at the Epcot resorts. I'm sure it's the number one problem faced by the gate attendants at these resorts. It's a problem if you've paid several hundred dollars a night to stay at these resorts and have trouble finding a parking place. It wouldn't be a problem if you were the only one who thought of doing this. But you're not.
I admit it's tempting and seems harmless. My own DW suggested it last year when we had a 5:15 AR at Kona Cafe before going to MK for the Christmas Party. I told her it was a no-no and she got miffed. I decided to drop off her and the boys at Polynesian, and told the gate attendant we had a reservation. She gave us a 3 hour pass, and told me to drive away from the gate slowly so she could write down my license number. If I had any doubts about parking there while we were in MK, that cleared them up! So I drove back to MK parking and walked back to the Polynesian. A little inconvenient, yes, but not as inconvenient as being towed. (And yes, that does happen.)