Yeah their messaging is a bit strange. Perhaps someone with more info on Arc can clarify, but their landing page makes a strong point about them being privacy-conscious, and their summary of their own terms of service is "TLDR: we won't spy on you", but at the same time you must log in to use the browser. What is their monetization strategy? If something is VC-backed and free, it's hard to believe that they aren't ad supported in some way, which almost always relies on some amount of tracking.