iPad Air M2 battery drops from 80% to 15% in 3 hours - continued

So, as my earlier post said “iPad Air M2 battery drops from 80% to 15% in 3 hours”, I still feel something is fishy. While it took less than a year to fall to 87% capacity, it has maintained that level for a very long time. Why doesn’t that level continue to fall? Is this a way for Apple to avoid replacing the battery?