Yes, they sold with a 14-50 plug but I don't remember it supporting 40A charging.
However you are correct. There was a thread here about it:
I see the corded UMC is currently out of stock and the price has been lowered from $520 to $400. https://shop.tesla.com/product/corded-mobile-connector Can anyone hazard a guess as to what's going on with this MC? Could they be getting ready to update it with a 24 ft cable as they did to the...
teslamotorsclub.com
I found the old URL
https://shop.tesla.com/product/corded-mobile-connector. But it's now 404.
However, the web.archive.org Wayback machine has the page and the owner's manual.
The Corded Mobile Connector features a NEMA 14-50 plug and improved charging speeds in comparison to the Mobile Connector with NEMA 5-15 Adapter. Includes: 1x NEMA 14-50 Corded Mobile Connector - 20’ cable 1x storage bag Corded Mobile Connector Manual Note: The Corded Mobile Connector is...
web.archive.org
It shows maximum output of 40A.
The V1 UMC would support 40A, but the V2 UMC is 32A max.
One reason to do that is that a 6-50 or 14-50 socket only guarantees 32A. It can be used with a 40A breaker.
Not what they were asking about.