What Disney doesn't want is having people park for free at a resort near one the parks and get away with not paying the parking fee at the park. Much of this seems to depend on how busy they are, what time of day it is, etc. For example, if you show up at 9 am, they are probably more wary of someone who actually wants to spend all day at MK in addition to just having an ADR. If you show up later in the day and/or at a time when they aren't as busy, that might explain the differences some are seeing.
I am sure the Disney guards have heard every excuse under the sun from people trying to park for free !!!