You can google around, these batteries don't use full capacity, instead they have a buffer that kicks in for failed/worn cells.
I'd like to see the behaviour near the end of life for these packs.
Packs in laptops seem to last 3 hours, 2 hours, 1 hour, then 5 minutes, 5 seconds, and "won't even switch on". I wonder if the car packs will have a similar performance cliff.
It's more to reduce degradation - lithium batteries don't like being at <20% or >80% state of charge. If you never let them get there, they will last a lot longer.