Though reading the specifics there, it looks like Google's adapters in particular should work with any other phone because they can handle analog or digital signals. So they're doing well.
It's unfortunate because it's the "USB-C standard" not to do analog through the pins, but I think this a case where it's ok to break the standards. I'm not sure if there are any IEEE fines for that though.
Other manufacturers are doing... less well.