If the URL is your state container, it also becomes a leakage mechanism of internals that, at the very least, turns into a versioning requirement (so an old bookmark won’t break things). That also means that there’s some degree of implicit assumption with browsers and multi-browser passing. At some point, things might not hold up (Authentication workflows, for example).

That said, I agree with the point and expose as much as possible in the URL, in the same way that I expose as much as possible as command line arguments in command line utilities.

But there are costs and trade offs with that sort of accommodation. I understand that folks can make different design decisions intentionally, rather than from ignorance/inexperience.