You're getting a scattering of answers that are all basically correct, but are maybe not putting the whole picture together.
Since the appliance being plugged in will draw 32A continuous, a 40A breaker would be acceptable by electric code. It does allow for that exception of a 50A outlet type on a 40A breaker for this reason and because there is not a 40A outlet type.
But the reason why a homeowner would be asking for a 50A rated circuit anyway is basically just to do it the better "more right" way instead of the bare allowable minimum. If a future buyer of that house wants to use that existing 14-50 outlet, it would be helpful if it is installed with the full regular expected capacity, rather than just with the thinner wire of the 40A exception case. What if they want to use an RV that could use more current? What if your UMC breaks, and you find a fantastic deal on a Juicebox or a Tesla corded mobile connector or Tesla brings back the pluggable wall connector or something that can plug in and pull 40A continuous? You'd be irritated that the initial bare minimum is now a limiting factor.
Or what if a friend or relative with an electric car (or truck?) comes to visit at some point a few years from now, and they have a 40A cable and could use the extra charging speed?