I think this is one of those things that seems more like a gimmick. Your AirPods charging case has 24 hours of use. I use my AirPods all the time and the case seems to take forever to run down. I just don’t see a situation where I would give up phone battery to charge my AirPods case. Apple is making the iPhone battery last longer but not 100% of that is because it’s a larger battery. The iPhone battery is still significantly smaller than a comparable android phone battery. I mean maybe if they can make this feature included without significant cost increase