Yeah, but that’s after the fact, and after their content has federated to other instances.

It doesn’t solve the bot problem, but just plays whack a mole with them, whilst creating an ever large amount of moderation work, due to it federating to multiple instances.

Solving the bot problem means stopping the content from federating, which either means stopping the bot accounts from registering, or stopping them from federating until they’re known to be legit.