Chuck is right, and it appears the info posted is several years out of date (or from an old cached web page if was located with a search engine). Anybody can book at 180 days, regardless of where they are staying.
The ADR booking dates have nothing to do with
DVC. Any guest at any onsite DISNEY resort can call 180 days from arrival and book up to ten days from arrival. It's called 180+10, and it was instituted a couple of years ago as an incentive for people to stay onsite.
You should know, however, that not all of the restaurant availabilty is there during that +10 period -- only a portion is. So if you call and don't get what you want during that +10 timeframe, call back at exactly 180 days and you'll probably get it.