OK, so I asked the local FB group, as people suggested, and here’s the deal on the inaccessible wheelchair-accessible swing.
It was built by parents of a disabled boy. They got a grant and some donations from local students to build it. So the swing is for their son to use, and they don’t mind other disabled kids using it in their presence.
People are very proprietary.
This is a very sick boy with a rare brain disorder, so I don’t want to criticize the parents.