IIRC it was simply called Reason at first but then the slightly more descriptive ML was added for better searchability. People call it both Reason and Reason ML now. That seems fine to me :) You are right it mostly is just a different syntax for OCaml but like in the Erlang/Elixir case there is a bit more to the story (js interop, js ecosystem, new ideas here and there, more diverse community as a result, etc).

I still call it reason, especially when I talk about it with other js developers ;)