Does the Plex Dance cause library to re-run thumbnails, credits, etc?

I would usually agree with you that changes to the file shouldn’t require a plex dance. But I’m going to be completely blunt, if you know how databases work, there is no reason why the “date_added” field would/should be updated by any function, so this is a problem (■■■■ up) that you created for yourself. So don’t lay this on Plex.