The law doesn't directly stop anyone from doing anything, it acts much differently from a technical control. The law provides recourse to people hurt by violations and enables law enforcement action. I suspect Meta has since stopped their torrenting, and may lose the lawsuit they current face. Anyone certainly could log in to any site with credentials that are not their own, but fear of legal action may deter them.
Going back to Napster hasn't the gray area always been in downloading versus uploading?
If anyone could show that LLM companies have been uploading torrents then they really would be in trouble. If they are only proven to have downloaded torrents they're walking the line.