Believe whatever you like. I generally believe the US Dept of Justice, Civil Rights Division, to be a credible source.Technically I don't think ECV's fall under that since they're not necessarily a mobility device and in many cases are a "convenience" device as the name implies. ECV's aren't just for people who are disabled, but also for people who just have a hard time walking or standing for long distances/time.
This part of what you posted pretty much makes it useless to ask assuming they legally can:
I think there's probably some other legal aspect that aren't being addressed. I say that because Disney and other companies doing business in the area are very adamant in their training that you cannot ask if someone is disabled or ask them to show proof. Again though it's all kind of irrelevant when they're marketing these devices as a convenience and allowing anyone who wants to to rent them for any reason.
They could ask. They are choosing to not ask. For reasons I can only assume. Which I won't."any mobility device powered by batteries, fuel, or other engines… that is used by individuals with mobility disabilities for the purpose of locomotion, including golf cars, electronic personal assistance mobility devices… such as the Segway® PT, or any mobility device designed to operate in areas without defined pedestrian routes, but that is not a wheelchair"