> I was answering the question of “how do I discover another host’s mDNS hostname?” It turns out that is a per-service question.

No, it's not. That is a service address, not the host's hostname.

The host's hostname is whatever the computer is named, which if you are in a position where you're wanting to give someone else its IPv4 address or access your own thing via its IPv4 address you definitely can also know it's hostname because it's either shown in the same parts of the GUI or one command away. On a lot of CLI systems it's literally in the prompt.

Either way it's not advertised unless that host is configured to advertise itself, you have to query for it and the host will then respond.