I’m not saying one is a requirement for the other, just that you don’t have to worry about the battery-removed state when it doesn’t exist.
From the tear downs I’ve seen, it seems like the primary motivation for the non-removable battery is so they can cram it into every spare piece of space.
I guess there are also multiple states of removable. 2012 macbooks had the battery in multiple packs in odd spaces like the new ones but they had a screw in bracket holding them in place which made it trivial to remove and put a new one in. The new ones have it glued down so heavily that the battery replacement process is "Take the screen off, put it on a new bottom case, throw out the old bottom half"
From the tear downs I’ve seen, it seems like the primary motivation for the non-removable battery is so they can cram it into every spare piece of space.