I would say yes, but qualify that by noting that database is a very general term.

What kind of database it is, and who its target user is more revealing, but unfortunately my best guess is tautological. It is this kind of database for this kind of user.

Regarding number two, we can see that ssb isn't the right tool for every job. Maybe social database is an appropriate term?

I'd say "yes"
It's an interesting hybrid of protocol + database.

It's a subjective database, not a universal one.

secure-scuttlebutt absolutely aims to grow into a pretty good decentralized database,
but because it's decentralized that means it's gonna turn out pretty different to say, mysql.

The fundamental difference being that in a decentralized database, "permissions" are enforced by the reader, not the writer (or rather, receiver of the write - "the database")