Treated how? Universal Studios Hollywood provides a Shuttle Tram service to both Hotels, seems like they treat them as part of the area. (Not a resort since it is only one park, unlike Disneyland, Knott's and Six Flags California).
There may be a shuttle agreement but as I mentioned above when you look at the hotels' websites there is no mention of being "onsite" hotels or having any other kind of official arrangement with the theme park.