They absolutely are verification. If they weren't they wouldn't need to look up a json file on the supplied domain to provide a tick or cross (if failed to verify).
Discussion
It's verification that a file and a field exist. That's it. It's not verification in the traditional sense of verification like on every other social app.
Yes, but if you own a domain you guarantee that it is you. E.g. Will has multiple impersonators, but they can't verify using his domain jb55.com so you do actually know it's him. This level of verification is only important if you need to establish trust. I don't so the existence/ verification of my nip05 is unimportant and at times has been broken with no real effect on my or my mutuals experience.
I suppose this is a difference between it technically not being a verification, but as a first impression / process, but in reality feeling like it is some sort of verification process.