I would try one more time for the most advanced members:
1. Battery capacity degradation caused by normal wear and tear - is not a defect and there is nothing to worry about as warranties for all EV cover those entirely and they simply would never have any warranty claim to deal with and none of us should worry about as it is small/slow and it is the best case scenario for any EV owner and EV manufacturer.
2. Battery capacity degradation caused by not normal wear and tear is a defect. This condition usually due to one or more battery cells, the battery comprised of, premature failure ergo it was caused by a defect in manufacturing of those few bad cells. Most of EV batteries cells are perfectly fine, just one or two can abruptly make battery only half or third capacity, specifically in batteries designed with prismatic cells. It is pretty easy to prove this fact as battery test would reveal those bad cells.
3. Some batteries are serviceable, like in Ionic. Good engineering means those cells or modules of cells with bad cells could be replaced very economically. For example Ionic has most of the HV battery components serviceable and anybody can buy any battery component: https://www.hyundaipartsdeal.com/parts- ... m=37371A13
It seems only few companies replace a whole battery, but better off, they need to replace engineers who designed those dumb, expensive liability monolith traps.
So no, Hyundai/Kia would never need to replace the whole battery. Hyundai/Kia would just repair your battery very economically.
4. Degradation is only one of the aspects to worry about, there is plenty of other bad things that could happen to the battery, burned heaters, relays, sensors, BMS controller and etc. Just tiny temp sensor failure would make BMS to disable the whole battery, without any regards to the remaining capacity. Would you rather change the sensor or replace a whole battery? Lifetime EV battery warranty to the original owner who keeps car(s) for long time is a great thing to have. The secondary owners would also benefit as they could repair the battery economically as well.
I guess most of the concerns on Leaf forum are originating from the past Leaf battery issues, but it does not mean it is universal to all EV batteries, their design and manufacturers.