I’ve never understood the claim that CMB homogeneity implies those regions need to be causally connected in a traditional sense; they might be “causally connected” by the fact that they obey the same physics. Even if you don’t accept that the physical laws themselves could be spread over a spacelike boundary, it could at least appear that way due to selection rules (the same way entanglement collapse can appear superluminal without being so under MWI).