I'm not sure that's true. It's important to note that these bans are from the Bluesky App View (one component of the infra), and that these users can continue to post under their identity (if they own it, which they can), and users on App Views that haven't banned these users could continue to follow them.
None of that works with Mastodon. An admin bans you from the instance, and you can no longer post, use your identity, interact on the platform, etc. You have to start from scratch.
In short, Mastodon reduces the blast radius, but the "blast" is the same as on any private platform. Bluesky/AT Proto changes the impact to a different, strictly lesser type.