However my understanding is the new Lithium Iron Phosphate (LFP) batteries support a higher Model 3 RWD charging rate. I was told by Tesla that when I receive delivery of my Model 3 next month, it will be from the Freemont factory, which has switched from the older Nickel Cobalt batteries to the new LFP batteries for the Model 3 RWD. I've heard from several sources that Model 3 with LFP batteries supports a faster charging rate. Just not sure if that would translate to me seeing a difference the a 40 AMP Mobile charger with a built in 14-50 plug. If it does, I will then purchase the 40 AMP version of the Mobile charger.
I think you may be mixing up a couple of things (or tesla may be mixing up what you are asking).
SR+ tesla model 3s level 2 charge at 32amp maximum... full stop. There is no tesla SR+ / Standard range / LFP that charges at faster than 32amps on Level 2 home charging. Do not pass go, do not collect $200.
Now, its possible that a LFP model 3s can DC fast charge (which has zero to do with your mobile adapters / wall adapters etc) faster than non LFP SR model 3s, but I havent been following that.
With that being said, for your home charging, the car will not charge faster than 32amps. Period.
Edit... I didnt see that @ucmndd said basically the same thing. I wasnt attempting to pile on, but will leave my response here.