"It's OK if the number of secondary fediverse services¹ is much less than the number of accounts or the number of primary account services², as long as it's much more than one."
¹ for example: people search, text search, tag search, bridges, groups, reposters
² for example: Mastodon, Friendica, Pixelfed, Pleroma instances
I'll take for instance the number of services that help you find your Twitter social graph on the fediverse. I know of Debirdify, Fedifinder, and Movetodon.
There are probably a few more I don't know of, but I doubt there are more than about 10 publicly available.
There are about 10-20K primary account servers on the fediverse.
There are close to 10M accounts on the fediverse.
So roughly 1::1000::1000000 proportions there.