They can flag the accounts and shadowban based on metrics. Keeps them in total user count, might drive more signups too afterwards. They know who writes "fuck spez" in comments, but they don't know which accounts are run by single people or coordinated groups. Place potentially provides some of that information.

Reddit wants users who engage authentically with content, generate interesting content, and interact with ads. High-intent users, not people who coordinate to post "fuck spez" and bad-mouth Reddit.

Whether they're forward planning enough to realise that is another issue altogether.