wp-api didn’t has any route for new user registration as the route
/users requires authentication for create operation
As far as I know, using proper authentication (I’m using JWT), rest API does let you create new users.
The problem is that if you go that way, you have to implement your own mail-verifcation system, since no confirmation mail is sent.
(See my answer to this: Authentication for a mobile app connected via wp-rest api?)