Actual accessible rooms are a booking category.
However, it is possible to fit an ECV, and depending on the room and one's creativity, possibly two ECVs into non-accessible WDW hotel rooms. For example, the disabilities thread has pictures of two ECVs in a Pop room. To make it easier, you can call housekeeping and ask that the table and chairs be removed from the room.
FWIW, I have fit an ECV into a WL room, and I think if the table and chairs were removed you could get two in -- but it takes some work and strategizing.
So the question becomes, room size aside, do you need the features of an accessible room, or is a standard room sufficient ? For example, many of the newly refurbished rooms have walk-in showers. Since you need a walk-in shower but perhaps not a wheel-in shower, they may have normal rooms with handrails or be able to install handrails if requested.
This article has quite a few photos of a king refurbished room, including showing the shower:
https://*****.com/2019/07/photos-video-newly-refurbished-rooms-at-disneys-animal-kingdom-lodge/
Contact Disney to see what they can do for your based on what your needs are:
See
https://disneyworld.disney.go.com/en_CA/guest-services/hotels-accessibility/
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Services for Guests with Disabilities at Disney Resort Hotels
A variety of helpful services and access options are available for Guests with disabilities at Disney Resort Hotels.
For more information, please contact Disability Services at (407) 560-2547 or email disability.services@disneyparks.com.
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And
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How to Book an Accessible Room
Please select the “Accessible Rooms” checkbox when you book your vacation online to view available accessible rooms.
If you would prefer to book over the phone, please call (407) 939-1936.
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As for ECVs parked unattended in the hallways:, the two main issues: (1) fire hazard -- they block the evacuation route for everyone should there be a fire or other need to evacuate the building, becoming a hazard and narrowing the egress pathway; basically, a fire code violation. Hallways have to be a certain width and with the ECV parked unattended in it it isn't wide enough. (2) people can mess with the ECV, from stealing it to "relocating" it to vandalizing it to just unplugging it. You are responsible if anything happens to it, but aside than that, *you want a functioning ECV so you can enjoy your trip*.
SW