An accurate depiction of what's at risk here. I think that the anti-Meta pact is misguided however, as pre-emptively blocking Meta instances and then blocking any non-Meta jnstance that doesn't take part would rip the Fediverse in two and make it all the easier for FB to embrace, extend, and extinguish it, having already split the fediverse into two sides.
I think that Meta joining the Fediverse represents a very real threat to our experience here, but I also don't think preemptively blocking them is going to have the desired effect.
The instances that are adopting a wait and see approach have it right. Make it clear that the fediverse isn't own by anyone, and then continue to act like it. Defederating seems like surrendering huge swaths of the fediverse to Meta.