They really eliminated this a few years back and said that one could not keep the same room type at same resort to avoid getting the dining plan for entire trip,
One of the reasons that they will link a reservation so you don’t have to change rooms is if it’s made on two different memberships. A note is placed on each.
In your case, you can’t have them linked because There is no reason not to make them one. Which means, the reservations go to the room assigner as their own and good chance you have to move,
But, when I have had this, close to check in, they have combined the reservation into one..without notice. It was about a few months out.
They only time they didn’t was when I had a waitlist set up for those nights. I think they realized I was hoping to split stay. Once it didn’t come though, I called to merge.