It even cooler than that: You only have to standardize the types and meanings of the links, the actual implementations can vary in the locations of the endpoints, but the structure of the documents can too, and the client(s) will be smart enough to figure out that on this server they need to retrieve /users/mike/products/, and on that server they need to get /userproducts/mike/all/, just through the fact that the representation of the user (also probably retrieved from different locations) on each server has a link labeled rel="all products" pointing to the right place, regardless of what else was included or omitted from the representation, so you can have interoperability on whatever is standardized even if implementations of both clients and servers have different capabilities they expose.

So, as long as you standardize the semantics and relations, the URL layouts and the document layouts can be quite different, in the same way that you know when looking at a page what the button or link labeled "Home" will do, regardless of the exact location on the page or the fact that on one server it takes you to /, on another to /index.html, and on yet another to /main/home/ .