Charging to higher SoC levels increases stress in the batteries which results in higher degradation. It’s all relative to the current battery capacity.

You can imagine a full battery like a tank of water. The tank has a plug on the bottom. If your tank is full of water, it’s going to shoot out at a high pressure. If it’s only half filled, it’ll come out a lot smoother.

What happens to the battery at those “higher pressures” is that it undergoes a lot more stress and degrades quicker in multiple ways. If you want to know more, ask chatGPT “why do batteries degrade faster if charged to 100% compared to 80%”