Ten and over are only considered adults for the parks. For the resorts the are still children until the age of 18.
Even if that wasn't the case, as long as you are buying a product from a company, they can set terms and conditions for that sale. If Disney wanted to state that kids had to be 14 years and older to stay alone in a room, they could. You would have the right to then not rent a room from them.
I was just saying they should treat them as adults if they are going to charge them adult prices. I wasn't saying they couldn't make their own rules. Geesh people just like to argue. I mean there isn't many circumstances a company could charge the same amount to someone and not give the same thing because of their age. For example I order chicken tenders and fries off the adult menu and my ten year old also orders the same off the adult menu, we are both charged the same, but she gets less because she's a kid. Same principles apply here.