I'm curious as well. I looked at the press kits for my 2020 vs. the 2023 and the mileage did come down from 215 miles to 212, but I know the EPA has also changed how it does those mileage calculations, so I wonder if the numbers would be the same or not.
The non-plus Leaf still shows as 149 miles, exactly like my wife's 2018 showed when it was advertised for sale. Going from 215 to 212 wouldn't compute for the change if they really took off 2 kWh worth of capacity from the battery as a whole. The 40 kWh battery packs only reserve 1 kWH at the top for driving, so the owner can use nearly 39 kWh of capacity. Is that shortening the battery life, hard to say since my wife is over +50K miles on her 2018 and she drives it dead, a lot and also charges it to 100% and forgets about it, a lot.
Somehow, her battery SoH is still above +90%
For the EPA mileage to come down, all things being equal, the +plus Leaf would have to be only charging to around the +56 kWh mark, just like mine, which would mean they are still leaving nearly +4 kWH at the top.
It's also possible that all of this math is moot because it's just the marketing people that are bad to presenting the facts.