Fielding isn't saying the client should know nothing about the meaning of the responses. He's saying that what the client knows about the meaning of the responses is derived by interpreting them according to the media type, which doesn't have to be HTML, rather than, for example, by looking at the URL. Quoting from what Fielding wrote in his post and comments:
> A REST API should be entered with no prior knowledge beyond the initial URI (bookmark) and set of standardized media types that are appropriate for the intended audience (i.e., expected to be understood by any client that might use the API). ...
> When I say hypertext, I mean the simultaneous presentation of information and controls such that the information becomes the affordance through which the user (or automaton) obtains choices and selects actions. Hypermedia is just an expansion on what text means to include temporal anchors within a media stream; most researchers have dropped the distinction.
> Hypertext does not need to be HTML on a browser. Machines can follow links when they understand the data format and relationship types.
That is, htmx.org or intercoolerjs.org might argue that "HATEOAS is [exclusively] for humans", but Roy Fielding doesn't agree, or didn't in 02008.
— ⁂ —
While I'm arguing, I'd also like to take exception to the claim that this discussion is irrelevant to anything people are doing today. It's an "old person battle," as some say, in the sense that old people are the people who have enough perspective to know what matters and what doesn't. REST matters, because it is an architectural style that enables the construction of applications that can endure for decades, permitting the construction of applications that evolve without a central administrator, remaining backwards-compatible with decades-old software, and can include billions of simultaneous users.
This is an important problem to solve, the WWW isn't the last such application anyone ever needs to build, and JSON RPC interfaces can't build one.
The trouble with redefining "REST" to mean "not REST" is that the first step in learning known techniques to solve a problem is learning the terminology that people use to explain the techniques. If you think you know the terminology, but you have the wrong definition in your mind, you will not be able to understand the explanations, and you will not be able to figure out why you can't understand them, until you finally figure out that the definition you learned was wrong.