I don't believe this has anything to do with 4680 cells and is a misunderstanding of the urban Dyno testing and how it is used to estimate range. You can read more about it in the link below but the short of it is that a ~30% reduction factor is applied to this raw mileage number to get to the published range which jives fairly well with Tesla's rated range on their cars.
How Tesla puts distance between itself and the competition while still playing by the EPA's rules.
www.caranddriver.com
In general, Tesla has 0 reasons to increase range with the backlog they have when they are battery limited. 4680 cells will mainly be good for Tesla and help them produce more cars by using less battery materials per car.