Bed heights are inconsistent because, up until recently, there were no guidelines for bed heights. Even in the same resort, different rooms can be at different heights.
If the bed is too high, there are a couple of options.
One thing people have done is contact Housekeeping and ask them to lower the bed. One way they do that at times is by removing the bedfrme and leaving the box spring and mattress sitting on the floor.
Another thing is to actually rent a hospital bed for your stay. You can arrange it through Special Reservations or by renting fom a company on your on. You can find more about renting equipment in post 2 of the disABILITIES FAQs thread. That thread is near the op of this board or you can follow the link in my signature.
There is also a post about room/resort accommodations, which has the phone number or Special Reservations.
In either case, the resort will work with a rental company to get he equipment into your room before you arrive. They will move or remove any furniture they need to make room for the bed.