I wasn't wrong when I said someone would disagree even though I said that I ohmed it out and it wouldn't make any sense to sell an adapter that shorted the two hots. I have the piece on the bench in front of me. There is no connection between the two hots. It is as I described in #14 and it will, therefore, work.
Why is common sense so rare?
Well, actually, let's be more careful here. I am speaking of the TT-30 adapter that is sold specifically to allow charging Teslas i.e. as a Tesla accessory. Perhaps there are adapters that connect the two blades together for use when kluging a 240 V camper to a 120V plug. That would allow use of 120V appliances in the camper and disable any 240 V loads.
I think the message is to ohm out any adpater you currently have. If the two hots (on the 14-50 side) are common you will not be able to use it.
Note that there would be no danger were the camper adapter used to try to charge the Tesla but there would be potential danger of damage to RV 240V loads were the Tesla adapter used to connect an RV. So if you get a Telsa adapter be sure to mark it with bright red nail polish or something.