We are members at OKW since 1993 and always just reserve a regular first floor room. The one who uses a wheelchair is my DD who is not very large and doesn't require the other wheelchair accesibility.
The wording they have always used on our reservations was "Request first floor for Medical Reasons" or some very similar wording. The reason they use that is to be able to tell who needs first floor and who is just requesting it for some other reason. They fill the medical requests for certain room locations/types before they fill the general requests. It's possible that they changed the wording on their code for some reason.
The one time we did try a totally wheelchair accessible room, it was noted on our reservation that we had a wheelchair accessible unit. I don't recall for sure how you got in, but I'm almost positive there still was a whirlpool tub; it just was arranged to have steps and a rail or something. The shower in the wheelchair accesible rooms is just a tiled area without a door and a wheelchair or shower chair can be rolled right in. The slope of the floor is supposed to keep the water in the shower (notice I said "supposed to").
The shower is not in the same room as the whirlpool in the regular rooms or the handicapped rooms. The whirlpool tub is in a large room with just the whirlpool and a sink that are open to the master bedroom. The toilet, shower and another sink are in a separate room beyond that.
I suggest you call to make sure, but my hunch is they just re-worded the "These people have a medical need for the first floor" language. If you are renting thru DVC or are a member of DVC, you can just use the member services number. If you are renting in another way, then use Resort Special Reservations at (407) 939-7807 (voice) or (407) 939-7670 (TTY).