It seems like the battery packs on cars are engineered to manipulate people, and this would be an easy way of making two very different cars seem the same.
Lithium batteries degrade. With heat, with time, with charge cycles. Article after article writes about how Tesla's battery packs barely degrade! 8% capacity loss over 100,000 miles.
This has to be a lie. Unless they've come up with a new magical battery chemistry.
Lithium batteries degrade. 15-20% capacity loss per year. 2-5% per hundred cycles.
There are ways to cheat though, design your battery electronics to pretend to have a lower capacity at first and then gradually allow them to discharge more and more as the battery ages. It's true that there's a small boost to capacity retention if you don't fully discharge.
A new Tesla might well have an actual 400 mile range the day it comes off the lot, but they figure consumers would be really disappointed if that 400 mile range went to 350 after a year and so on... instead I'm guessing they pretend the battery capacity starts lower so that it's more consistent. In the end when they run out of spare room they'd initially left themselves the battery would fail fast.
What's to prevent a competitor to cut just a few corners on this strategy – don't give yourself as much future wiggle room so that you can say your capacity is higher?
I would actually love to be wrong, but what you see from the battery performance metrics just doesn't match up with any of my existing knowledge about how battery cells work.