Very hypothetical there, like you’re reaching for things that could go wrong.
I know that centralisation doesn’t work because I’ve seen it turn the internet to shit over the last 15 years. If I had it my way we’d go back to small independent forums with no federation because they were much better communities. But in the name of progress, federation does have some advantages, but as soon as things start getting too big there should absolutely be defederation to prevent the platform from getting like Reddit.