Apple often leaves little clues in their product design that hint at how they envision these products being used. I find that more often than not, it helps to think about why that may be the case, rather than rush to criticise Apple for apparently not thinking through the design of their product thoroughly enough.
The first clue I gather from the article is that bluetooth and "find my" is only disabled after three days. My guess is that Apple wants the AirPods max to remain discoverable via the "find my" app even when left outside the case. This will be useful for locating the headphones if they are misplaced or (more likely) when they have been stolen. There's no way for the thief to physically turn off the AirPods max and disable bluetooth / find my. At the same time, the user doesn't end up in a situation where he wants to locate his headphones and then goes "oh crap, I accidentally turned it off just now!"
It's always on and constantly emitting a bluetooth signal, just like your iPhone, iPad, Apple Watch, AirPods, MacBook, heck, pretty much every apple product that supports bluetooth and is capable of contributing to the "find my" network. This design sounds pretty darn deliberate (and clever) to me.
Either way, there seems to be no appreciable difference in battery consumption regardless of whether the AirPods max are kept in the case or not. Ultimately, the takeaway is - just use the headphones and don't worry about trying to micromanage its battery life.