Here's the thing I'm sort of seeing about circuit ratings, etc. If you install a 32A charger that requires the NEMA 14-50R plug, that needs to be wired for 50 amp service with a 50 amp breaker or it will fail inspection. Can you put a 40A breaker on a 50A plug? For inspection purposes, no, as stupid as it sounds. The only reason I can think of for that is if someone plugs in a device that utilizes 40A of current (80% of a 50A circuit's maximum), it will trip the 40A breaker since the plug is over rated, and people won't expect the breaker to be under rated for that type of plug. If you install the 50A receptacle, it needs to be wired with 6 gauge wire too.
General rule of thumb is to not exceed 80% of the working maximum of a circuit. That's why you see vacuum cleaners rated at 12A... that's 80% of a 15A circuit. That's why my Leviton 16A charger is rated at 16A - it's 80% of the 20A maximum. And the largest Leviton model they offer, which is at 40A, is again 80% of a 50A circuit maximum. If you bought the 32A Leviton charger and it was the HARDWIRED model, then YES, you can put that on a 40A breaker. 32A is 80% of a 40A maximum. But the 32A pluggable one will need to be wired on a circuit that is 50A through and through.
The ONLY type of branch circuit where a breaker can exceed the rating of the receptacles is with household 120V outlets. Most of those have up to a 20A pass-through, and if you wire all of those with 12 gauge wire, you can put the entire circuit rating at 20A, not 15 as the outlet suggests. However, you're not allowed to do this if you have a single 120V outlet that's rated for 15A on a 20A circuit... there must be a minimum of 2 outlets on a single circuit.
I did a lot of digging on that as I turned my 240 circuit in the garage to a branch circuit (more than 1 outlet).
I can also tell you this, UL, NEMA and NEC do not play well with one and other. I own an industrial systems integration business and we are UL listed, to follow UL guidelines it may impede on other standards.
You are permitted to install a higher rated receptacle on a less breaker, however after a little more investigation you are correct.
NFPA 70 - 625.40
Overcurrent Protection. Overcurrent protection
for feeders and branch circuits supplying electric vehicle
supply equipment shall be sized for continuous duty and
shall have a rating of not less than 125 percent of the
maximum load of the electric vehicle supply equipment.
Where noncontinuous loads are supplied from the same
feeder or branch circuit, the overcurrent device shall have a
rating of not less than the sum of the noncontinuous loads
plus 125 percent of the continuous loads.
32A X 1.25 = 40 amp continuous load = 50amp breaker
See ARTICLE 625 (Electric Vehicle Charging System) This is the 2014 DRAFT but it'd going to be 99.5% accurate or you can purchase a current version.