This debate was settled almost a decade ago. URL forms don't matter in theoretical dissertation REST, but 15 years of practice has firmly decided they are indeed a core part of real-world REST.
HTTP based web services existed before Roy's dissertation and while the formalizing of them helped them mature rapidly, the idealistic principles aren't the final word on the subject anymore. Real world practice now is.
My point is that APIs are an exception mostly because developers are conditioned by the RPC "APIs" mental models, which doesn't take effect when they're thinking about a "website" instead, not due to some fundamental technological difference.
And having extra irrelevancies to worry about such as "Version your API", "Use nouns, not verbs", singular versus plural, and nested resources are the consequences of being "practical".
HTTP based web services existed before Roy's dissertation and while the formalizing of them helped them mature rapidly, the idealistic principles aren't the final word on the subject anymore. Real world practice now is.