One big difference is the cost for users to follow someone.

In the old world, following a user to a different platform was prohibitively expensive for almost all, as you would lose everything. It goes against the network effect, and a ban from a major platform means people have to follow to a smaller network.

With Nostr, following a user to another relay is almost completely free, and with some elbow grease, can be completely automated away.

Fact is that there has not been a major test in this regard, nobody with a large following has been forced off relays, and if that doesn't happen, this is not a good comparison. Maybe the nature of Nostr is such that this will never happen, as trying to censor people by forcing relay operators to block them is a futile exercise to start with.