OK, I stopped by Tesla Service today, to try picking up the Plaid S Gen4 ECU. No dice. Not in stock locally, but it could be special ordered -- if I had a matching VIN to associate with the order. I have a 3, so no love. However, even if I did, would it cost the $150 that the Gen4 ECU did? Haha! Hell no - they wanted $450 for it
So, can't get it / wouldn't want it. Hmm. Wouldn't call it a dead end, but I'd really wish someone to try it if they have easier access to that part. Some wild haired folk with a refresh S as well as an older 3, want to try swapping ECU from Plaid S into the 3 and see if it reflashes & works with no fault, for science? Then see if it shows CCS compatibility on the "Additional Vehicle Info" screen (it should).
Doubt anyone would try that, but hey. For now I guess I'm back into waiting for Tesla's CCS adapter.