My current take on the issue is that REST advantages can only be realized if there a sufficiently smart client (aka human) driving the interaction.
However, I would add that I think you can build machine APIs using hypermedia, but the API contract would different. You would essentially define an OOP API with MIME Types as class definitions. That is partly I think why Toy Fielding put so much emphasis on defining those types.
But the real pwer of hypermedia - the ability to change those hypermedia relations dynamically - is really only useful for human-driven interactions.