The main culprit is that anyone estimating battery life in percentages. It's about voltage and current draw. The battery voltage can be read directly.
About being slow, I suppose it does run windows and its infamous 'defender'
No, I think it's fairly easy to see that a third of the charge suddenly disappearing is a fairly uncommon behavior.
Same for your Windows idea...
> The main culprit is that anyone estimating battery life in percentages.
I thought this was a solved problem, like, decades ago? At least I remember even the first gen MacBooks having accurate battery percentages, and it’s a more vague memory but my PowerBook G4 did too I think.