He's not talking about 80/20 limits. he's talking about material breakdown at extremes. Not all manufacturers spec in 80/20 limits. AFAIK, only Samsung actually lets you stop it completely at 80, the rest just try to let it sit no higher than 80 all night.

If they were saccrificing 40% of runtime to keep you from having to replace your battery, that would 100% be in the sales pitch.

And honestly, that article isn't a great source of truth. A number of the statements in there are inaccurate or, at the very least, misleading.

Charging beyond 100% or below 0% is mostly BS. The proper max voltage of the battery is a physics thing, they are in equilibrium at 4.7 / cell. Picking at a low power limit is up to the manufacturer and their choice in power distribution circuitry. He asked the chemist if you could overcharge or overdischarge a battery and mistook that as an answer that it was feasible to overcharge/overdischarge them.

"Leaving a charger plugged in at the wall and turned on wastes energy False (well, maybe a tiny bit)" This is still true for many chargers, and calling it out as a little bit in his own arbitrary numbers is disingenuous.

"Batteries perform worse when they’re cold False (mostly)"

Rest assured, your C rating is wildly affected by temperature; he's trying to again call it out as slight, which is making his own narrative.

"Powering off a device occasionally helps preserve battery life False"

The whole time your phone is on, you are charging or discharging. Those cycles wear on the battery any time you shut your phone off, you are in the least damaging mode for your battery, especially if it's around 50% or so.

"Using an unofficial charger damages your phone True"

100% BS, using a crappy charger might damage your phone. Buying a quality 3rd party chager is no problem at all.

The author doesn't appear to have a strong electronics background and he didn't ask the right questions or fully understand the importat parts of the answers

"And if too much current is delivered to a battery, that could mean ripping out too many of those lithium ions and leading to the same kind of degradation you read about earlier. That’s not to say that all off-brand chargers will be this bad, Griffith notes, but you’re still probably better off sticking with an official model." is not the same as "Using an unofficial charger damages your phone"

Article rests on one expert. That assistant professor's publication list doesn't seem to contain evidence about it, plus the quotes in the article don't directly say it happens.

Maybe it does, but that article only seems to be guessing based on (admittedly reasonable) theory.