What’s this actually mean? It’s not like they didn’t just switch domains and remain online? Article doesn’t mention any arrests so seems like they can just sidestep the domain seizure. Or am I wrong and there will be more action?

Yes but you will have to take extra steps to supply a valid cookie from a signed in account: https://github.com/yt-dlp/yt-dlp/issues/11296#issuecomment-2466538349