There are so very few accessible room with tubs that a request isn’t going to do much. I wouldn’t try to pinpoint the room number. Just let them know which building you would like.
Since the refurbishment, the beds aren’t listed correctly on TP. I went to see what our room in December was labeled as (1451 in the 50’s), and it was listed as 1 King + 1 Double with roll-in shower. In the description it said “1 King bed in room, with a layout that allows for a double-sized cot to be added by request.” It was actually 2 Queens (1 was the Murphy bed) and tub w/ rails.
I would just explain where you would like to be and why. As I said, there are so few rooms with accessible tubs that you probably wouldn’t get the exact room you requested anyway.