You are welcome to use the companion restrooms. But it is, after all, Disney, and I really don't see why anyone would be having an issue with trans or non-binary people using the standard gendered restroom...surely there is much more for them to concentrate on during their vacation. I remember while I was working and going to conventions....you know ladies rooms are always crowded and have fewer facilities than mens rooms, well during our short breaks, men used the mens room, and ladies just used both. There were closable stalls, they walked past the men, no one said anything. I mean, gosh, seriously, what do people think they'll see or do? I'm sure their imagination is much more interesting than the real thing. I know when I use the restroom, I sure don't care who maybe in the stall next door.
I remember back in the 90s, my Mom who was in her 70s at that time, used the restroom by the UK pavilion during Gay Days and was chuckling when she came out. She said there was a male using the stall next to her, and you could just tell it was a male. That was all she said. She really didn't think much about it. And we went on and enjoyed our day at EPCOT. I'm sorry that this still seems to be a major issue for some people in the 21 Century.