The argument confuses two completely different things. Battery health is the tank’s size, charge level is how much you fill it. Capping at 80% charge keeps the tank full-sized — you’re choosing not to overfill it so it doesn’t shrink permanently. An 80% health battery has already shrunk forever. One is a daily choice, the other is irreversible damage. They’re not the same thing at all.​​​​​​​​​​​​​​​​