I am an AP holder and currently have a room only reservation(with a discount) at CSR and the DDP without any additional ticket purchase. I think my agent referred to it as a passholder package.....so it can be done....
Bolding in your post is mine. As TDCNala said, AP holders can buy the DDP without having to buy park tickets, but the ressie then becomes a 'ticketless package', not a 'room only reservation'. The difference is that even though we can still get our room discounts and buy the DDP, the terms are different. With a room only ressie you have to pay only a one night's deposit and the balance is due at check in. When AP holders add the DDP, that room only ressie then becomes a pkg and the rules change. You don't have to buy a park ticket, but have to pay a $200.00 deposit and the balance is due 45 days out. Also there will be penalties or fees if you cancel or make changes.
AP holders can not keep their room discounts and also get
free dining though. We have to pay rack rate for the rooms and buy at least a one day MYW ticket. We've been every Sept since
free dining first started and just have to run the numbers every year to see which is the best deal for us (rack rate rooms with free dining and one day park tickets vs AP room discount and paid dining, and not having to buy those one day park tickets). If you stay in a Deluxe, the AP room discounts will usually beat free dining, but if you stay in a Value, free dining will always beat the AP room discounts. At a Moderate you just have to run the numbers, as it will depend on how many people are in the room.
For example, I've changed my upcoming May trip three different times. I originally booked at rack rate with the basic DDP. I told the CM I had an AP, so was able get it as a ticketless pkg (not a room only ressie, because I had the DDP). I had to pay $200.00 deposit (instead of a one night deposit) because I added the DDP, which changed it to a ticketless pkg. When we were at WDW in Dec, I called and applied the 35% off bounceback offer to it. I then had to also add a one day ticket, because that offer (like the free dining offers) required the purchase of at least a one day ticket even for AP holders. A week after I got home the AP discounts came out. I called again and switched to that, getting 40% off the room and was also able to cancel the one day tickets, because with the AP discount they weren't required, in order to buy the DDP. My point is that depending on the discount you use, sometimes even AP holders are required to buy at least one day park tickets too in order to get the DDP. In the case of free dining, not only do we have to buy one day park tickets, but we also have to give up our room discounts.