o.k....your dining reservations are not tied to your hotel. When they get reservations number that allows them to see your full information so they don't have to ask you for your phone number-they have it on your hotel ressie info. But the dining reservation goes with your phone number because that is the one thing everybody calling for dining reservations has...everyone calling do not have Disney hotel reservations...but everyone has a phone number so that's how the reservations are "filed" in the system.Yes the info on one reservation allows them to look at the other but they are not the same reservation so cancelling one does not cancel any other. That is why you get separate confirm numbers for your hotel room, and every single dining reservation is a separate confirm number: you can cancel any one of them and still have the rest.
We just did this recently for May trip...son cancelled his Disney hotel room, but kept his dining reservations when he was offered free room with a friend. All of our family dinner reservations are still in place even though the original hotel booking no longer exists. I know this for sure because we've called back twice to change them since the hotel cancellation. All of his dinner ressies are still there.