It's my understanding that PRGS represents register receipts. In other words, PRGS doesn't track who spent money at a hotel's restaurant or store, only how much was spent at that restaurant or store. (This does not mean that Disney does not know exactly how much you charged; only that they don't report it in PRGS.)Just one question for clarification if you will?
If the guest opts to pay as they go and not have room charging is their spending captured?
With this in mind, most Guests eating or shopping at most Disney hotels (e.g. Port Orleans Riverside) are staying at that hotel. Still, it's not perfect. Several Deluxe Resort restaurants attract a disproportionate number of non-resort Guests. I'm guessing the three Monorail Resorts and Disney's Boardwalk are the best examples of this.
Conversely, some extremely popular hotel restaurants (e.g. Beaches & Cream) are difficult to book if you are not staying onsite. Even if you are not staying at the Beach Club, if you are eating at Beaches & Cream, chances are you are staying at one of Disney's hotels.