it will matter though if a significant amount of users / communities is on their instances, if that happens and people then decide to defederate, that means the resulting community will be much smaller. Perhaps even so much smaller that it will eventually become a ghost town. It wouldn't be the first time something like that happens!

given that we know Meta is not to be trusted at all, it stands to reason to never allow them to grow big enough inside the fediverse that the aforementioned scenario could happen