Could be either/or. I long ago lost the brassiere that came with my AirPods Max (not really lost, I just can’t be arsed to dig it out of where I think it is) and they’ll drain themselves fairly quickly just trying to throw out stray connections to any of the five or so devices they can connect to unless I make a point of disconnecting them. AirPods Pro exhibit the same exact symptoms when the contact inside the case needs to be cleaned.
There’s a magnetic contact that the “bra” case engages that turns off the headphones so the battery doesn’t needlessly drain. Bunch of companies make after market cases/covers, you should get one of them at least.
I am aware of how it works, that's why I front-loaded the part about the brassiere being MIA at the moment. I just don't care, and I don't take it outside except on the airplane. Next flight I have, I'll probably dig out the brassiere.
Also in my experience, the brassiere was never perfect about guaranteeing the AirPods Max were put perfectly into a sleep state. The same exact issue could sometimes occur, maybe an alignment issue. The AirPods Max sound fantastic, but there's a lot of little details about them where Apple just kind of dropped the ball.
If Person A loses 1% over a week in standby, and person B loses 20% overnight, it's probably not the battery..
Unless Person B also tells you that in general their air pods only last 30 minutes playing music.
As stated, their percentage of power level fall vs person A is 2000% more being generous (person A said a week, not a night). If it was because of the battery, the air pods would also last way way way less playing music.
