Great article. I also thought about why we don't have the option to protect the battery when it's plugged in for the most of the time.
The sad thing is that this is really simple to implement, and they already have the hardware for it. They just need to read the voltage of the battery and then, based on the reading, they can continue to charge it or stop. The users should only choose when to stop/start the charging.
IMO the EU should ban all the laptops that don't have this feature. It encourages waste. We don't need more waste when dealing with climate change. At most, the price would increase with a few euros, but it would worth the cost.
Also, I would love for you guys to create a new section when you review laptops. When testing the battery, mention if the laptop supports a battery charging limit. And post the result in the conclusion as positive or negative. Like you do with the PWM for the display. Probably the best way to set the battery limit would be in the bios so that linux users shouldn't have to use win for that.
The same thing applies to smartphones. OEM don't allow to set a battery limit. But great news, there's an app for that and it works on most phones! It's called Battery Charge Limit and you can get it from here xda or fdroid. The bad news is that it requires root.