“Proper” use of a REST or hypermedia API generally requires you only ever initiate communications with the API from the root (https://my.api.example/ versus https://my.api.example/some/other/url). From there, every response from the API will then contains links to other resources, often with a relation to explain how each resource relates to the next. In this way, you never guess a URL - you are always given it.
Speaking from practical experience using an API like this: it can result in a lot of extra round trips to get to your final destination. The indirection is nice purity-wise, but in practice do you really want to make 3-4 times the round trips to the server for every API interaction? Especially when you might be on a mobile network? All for the sake of flexibility you may never need?
I'd say supporting the discoverability for learning, and consistency etc is nice. But in practice concerns like this (and the DHH example, and others already in comments here) will crop up and clients will start building their own direct URLs. So the idea that you'll be able to change the URL structure without affecting clients is a pipe dream.