OK, there's a little confusion here.
First off: The Tesla Mobile Connector has
never supported doing more than 32A @ Any_Voltage.
But there's a bit more to it than that. Take the following with a small grain of salt.
If one looks through the list of
available NEMA connectors one will notice that there's 15A connectors, 20A connectors, 30A connectors, and 50A connectors. There are, notably,
no 40A connectors.
As it happens, there are objects like clothes driers and electric stoves that need 40A.
There's this general NESIC (That's the National Electric Code standard) rule: The amperage of a breaker in a breaker panel, the gauge of the wire used to convey that amperage, and the socket must match. It's actually legal to have a wire gauge
larger than what's required, but not smaller.
The problem: Copper Costs Money. If one has an electric stove with a 40A requirement and one has to use a connector that can supply 40A, a 50A connector is all that one has. And that means, generally, using wire that has a 55A rating. (For various reasons, there's no copper available that's dead-on 50A.) Electricians hate spending money on copper. So, somehow, into the NESIC came this exception: If you have a 40A load, you can use a 40A breaker, 40A wire... and a 50A NEMA14-50 connector.
I don't know the full details. I'm guessing that the socket has to be labeled that it's a 40A load only, even if it does have that 50A look to it. But electricians Far and Wide have gotten really used to the idea that, when faced with a 40A load, they use 40A wire, 40A breaker, and that NEMA14-50.
Just to finish this off before we start the fun: If one has a constant, heavy load (hello, electric range and Tesla car!) one is not allowed to suck down more than 80% of the breaker/wire/socket rating. So, for a 50A circuit, this means a maximum of a 40A load. For a 40A circuit, this means a maximum of a 32A load.
So, imagine Tesla's problem: They have Zero Idea as to whether that NEMA14-50 one has plugged the Tesla Mobile Connector into has a 40A breaker and wire backing it up or a 50A breaker and wire backing it up. So, fairly obviously, they went for the Safe Option: Don't draw more than 32A on a 50A socket.
Couple more points, just so you know what you're working with, here. Amperage limits on wire are all about the heat. Power dissipated in a hunk of wire goes as Current*Current*Wire_Resistance. Note the "square" factor here. That goes into thermal energy. Which makes the wire warm. Heat energy flows away by radiation (hello, infrared!) and conduction, where conduction can include air circulation and physical contact. People with tons more experience and PhDs than any one of us here have placed wire in conduit, typical wall construction, and what-all and measured the temperature that the copper wire gets up to. Warm enough and it makes the insulation and such degrade. Degrade enough and insulation stops being an insulator, and Fires R Us. Ambient temperature and industrial vs. residential matters.
Finally.. that breaker in the breaker box is there for an
emergency. Run 120%, 200%, 400% more than what said breaker is rated for and it'll pop and save the day. Running it
right at its limit is frowned upon because, in almost all breakers, the widget that trips the breaker is thermal in nature: that is, it expands and pops the breaker. Even if a running 40A through a 40A breaker
might not pop said breaker right off (or after an hour or so), it certainly is going to make that thermal element flex. Enough flexure over time and, well, in the case of a real emergency, said thermal element
might not work. So, one needs to respect that 80% limit, they're not kidding.
A bit more. If one has a Tesla Wall Connector or the equivalent from $RANDOM_MANUFACTURER, it is presumed that one is not an idiot and is not using the wrong gauge wire for what one is doing. I happen to have a Gen II TWC in the garage; it's hardwired to a 60A circuit (breaker and wire), and so I can get the Teslas in the garage to charge at 48A, no problem. (48A being 80% of 60A). Likewise, if one has a 50A circuit, it's no problem setting the TWC (or equivalent) to that amperage value and charging at 40A. And so on.
Questions? We got answers.