My entire experience with hotels/motels (which includes half of the U.S. states, and six European countries) is that the matters under discussion in this thread are taken care of in a completely ad hoc manner- period. Whether you call six months in advance, and every week thereafter is, IMHO, totally irrelevant and futile.
That may be true for regular requests, but it is
NOT TRUE for handicapped accessible rooms with special features (like roll in showers) in hotels in the US.
If the guest needs those features and doesn't get them, it usually means they can't stay at that resort at all. For that reason, if a guest has needs for special accessibility and explains their needs before arriving, the hotel is required to provide an accessible room to them when they arrive according to the ADA. it is not a request, it is a guarantee. If the hotel has that type of room at the time the reservation was made, they are required to save it some way for that guest. If a hotel is not doing that for handicapped accessible rooms, they are not in compliance with the ADA (Americans with Disabilities Act).
In most hotels, that means those particular rooms are blocked off in some way so that they are saved for the people who need them.
In Disney's situation, when you call to make a reservation and tell the CM that you need accessibility features (in our case, a roll in shower), that CM contacts Special Reservations (SR), where the availability of those types of rooms is tracked. The CM at SR checks if any rooms meet the needs of that guest. If there are no rooms for that resort on those dates, the guest has the option of checking other dates or other resorts.
If there is a room that meets the needs and dates, the room is blocked at that point. The guest is TOLD that a room has been blocked for them.
The guest is supposed to get a confirmation sheet that says "Accessible Room Guaranteed". It IS a guarantee, not a request, because having the room with those features is
necessary for that guest to stay there.
We have been told many times in the past that Disney blocks a
specific room for that reservation, although the guest will not find out which specific room it is until they arrive.
The reason we have been told they do not tell the room is a room sometimes needs to be taken out of commission for some reason (carpet wet).
In the other post I made, I think the room we were assigned originally probably was the room we ended up with. BUT, the fold down shower seat in the master bathroom was broken - so that room had probably been taken out of commission, which was why we were told there were no roll in shower rooms available. For some reason, the roll in shower information was not in the resort's computer (although it was in the Special Reservation computer and we were told it would 'cross over'). They 'found' us an accessible room and we found out the shower seat was broken when we tried to use the shower (we reported it and they said they needed to order a new seat).