@elfile4138 I don't think you can A/B test the video (the "work") itself on YouTube? You can only A/B test metadata like titles and thumbnails which have a much higher bar to be considered protected work.
Regardless, copyright is a legal right and as far as my non-legal cat brain understands confers zero duty on the holder. There are limitations to your rights but I don't think being ethical about your enforcement methods is a limitation.
YouTube has always been a platform "for creators" which means right to be forgotten, etc. Hence they took out the dislike button, allow one to delete and reupload videos all they want, etc. Unless I have an ongoing legal case of subpoena I don't have a duty to keep record of what I said. I believe that's the legal part of it, this way YouTube keeps itself out of privacy/defamation lawsuits while making it a petri dish for malleable content with questionable COI and closed loop "optimization" pipelines.