It's not a scare tactic.
Blocking mastodon.social is now seriously on the cards for many admins, even ones who would never have done it before.
The reason the Fediverse exists is to be decenralised. M.s is way too large now, and getting even larger due to the official app's new onboarding.
If people want this place to be decentralised, they need to move off mastodon.social. If they don't care, then they can expect more fediblocks as m.s grows.