First of all, let me state that I am certain Chic tail is dominant to Swanky, and that it will eventually be proven to be so.
Unfortunately, I see an issue with the attempted proof posted here that I haven't seen resolved, The problem is that the proof that Cat "C" is pure is missing one thing; proof that Cat "C'"'s paternal grandmother (9t, Salt, Belli, Twink (ID: c0175986-4f0e-fdbf-8b4e-34627fb8490a)(hopefully I typed that correctly lol)) is pure Shorty tail, or at least that her hidden tail is no more recessive than Swanky. You see, if she hid a more recessive tail than Swanky, and it got passed to her kitten (Cat "C"'s paternal grandfather shows Shorty tail, so it could have happened), and then to Cat "C", Cat "C" would no longer be pure, and that hidden tail trait recessive to Swanky could potentially pass down the entire line. A highly unlikely scenario, for sure, but one we have to take into account when we consider whether something is "proven" or not.
If you can show me proof that Cat "C"'s paternal grandmother isn't hiding a tail recessive to Swanky (I looked at the above screens carefully and couldn't find it, but I'm not perfect lol), please show me. It would make the proof complete.
Thank you to everyone for your efforts on this. Hopefully this will be proven soon!