I think the whole thing has been taken out of context. The Disney site is telling non Boardwalk guests not to drive over to the Boardwalk and park in the self parking lots. No, it's not the best language but Disney is not going to say "hey, people! if you aren't a Boardwalk guest, don't park in the Boardwalk self parking area!" So the communication is done to not make other guests feel stupid.
If, as a Boardwalk guest, you want to park in self parking and not pay for valet, then you should be able to do it. If you can't, talk to the parking lot attendant and see what options you have. Don't bother to call the resort because you aren't talking to someone there, you are talking to a call center. So, there's no need to concern yourself with this until you are actually there.