Deriving a presentation layer from an API definition has no bearing on whether the client has to be stateful or not. The key difference for 'true' HATEOAS is that the API schema is sufficiently descriptive that the client does not need to request any presentation layer; arguably not even HTML, but definitely not CSS or JavaScript.
https://ics.uci.edu/~fielding/pubs/dissertation/rest_arch_st...
> any concept that might be the target of an author's hypertext reference must fit within the definition of a resource
