The 2-bed doesn’t come up as available because you have the studio held whilst modifying.
If you don’t want to risk dropping and rebooking, and I don’t blame you, then you could put a note on both that you have both a studio and 1-bed and “could they please try and get you them connecting”. I don’t know what the odds are. Room assignments are done centrally, whether they would have the nous to be able to oblige I don’t know.
I don’t know of they have a work around to this. It might be they’d have to do the same as you would, drop one and rebook. And somehow stop the waitlist process. But there’s little incentive for them to do it anyway. You have both rooms and it’s more expensive, points wise.