There’s a React team. I’m on that team. We develop React. Facebook uses it all over the place.
There’s also a Reason team. (Its creator also wrote React originally.) They work on Reason and its React bindings. Facebook uses it in some places.
We talk to the Reason team of course. But there has never been a plan to force all React users to use Reason. I don’t know where you heard that. If you like it, that’s cool. If not, that’s cool too. We’re just sharing what we use.
I’m not sure what your practical concerns are (are Reason bindings or TS typings not good enough?) but I’d like to hear them!
Of course I know “about” ML and TS. If I didn’t know about them I wouldn’t mention them. :-) I haven’t developed anything meaningful in either of them but it’s not like I’m clueless about what types are. I’ve been using C# for years.