I received my 2/2020 built MS LR in March. It arrived charging a maximum of 372miles. I was told at pickup over the next couple days several updates to the car would take place. one of them was a software update that would show "Long Range Plus" and the next 100% charge would be to 392 miles. That was 220.8.? I recently did a 100% charge with 2020.20.12 and it is still 392 miles range. The new 2020.24 update was just announced and I don't have that yet but Tesla announced the latest 100% to 402 would be coming in the next update to software. This tells me it is just a recalculation of range we already have in the hardware.
I don't know anyone who has actually tested the full range to these distances. Seems pretty silly to me because who would try to drive until their battery was dead? What's important to me is how much range do I get in the usable portion of the battery? That is probably the range with 25 miles reserve if the next Supercharger is less than 25 miles away. Otherwise more than 25 miles. Even more important to me is how long will it take to add 370miles of driving distance at a supercharger. Ideally, no longer than it took to fill my gas car for 370 miles of range on a road trip. That is the more important goal to me which is probably being throttled by the Supercharger capacity and the tapering management in the car. And this is only really important on long road trips where I may drive for 12 or more hours a day.
A potential Tesla buyer was asking me about this not long ago and after explaining how EV is different from a gas car, they realized the range is no longer a big issue even for road trips. It's like worrying over whether your car has a 12 gallon gas tank or a 14 gallon gas tank. Rate of recharging rather than range becomes more the concern on a road trip. Tesla owners love to make excuses for recharging time claiming they need to eat every 90 minutes or walk the dog, or pee. Maybe so, but that doesn't apply to everyone. Besides, highway rest stops don't have Superchargers and many superchargers are located far from the highway exits. That needs to change in the future with fast DC charging at every gas station. Buy gas, diesel, food, electricity and we're all happy.