Are they actually, though?

If they adhere to the RFC, yes: https://www.rfc-editor.org/info/rfc8615/#section-3.1

And https://www.rfc-editor.org/info/rfc8615/#section-3

> Applications that wish to mint new well-known URIs MUST register. them, following the procedures in Section 5.1 […]

Of course this is all voluntary, but why would you risk a name collision with another project if the process is quite straightforward?