Most colleges have a waitlist, and that is why they have it so if a kid that accepted backs out. Ten will get you twenty that they are now going to pull from their waitlist and offer a slot to another kid. That kid at this time has put a deposit somewhere else, and if this was the dream school they are going to jump ship too.
Now if that is the case than I would say to them, so now if roles were reverse and they got a call from another school, what exactly would they say or do?
I also find they are being non-sensical. For example, just like SA appointments they offer more slots than they expect to show up in the fall. I know for my DD that went to VT and my DS at GMU they have historically close to 0% come off their waitlist because they have a high enough percentage that accept their admission offer. Point being that most colleges would love to have more kids like yours where you pay the deposit knowing that if they call at this late date they are going to lose that deposit. It is free money for them while at the same time creating up space in the dorms (instead of tripling up a double, thay can keep the dorm room that is meant to be a double a double).
~ Hint if they do call, pull out that congrats admission letter. Typically it will say how many applied and how many admitted. Than flat out ask them how many do they expect to show up in the fall? IE if they admitted 4K, but really only want 2500 to show up, than I think they should be more than happy that they get to keep your deposit.