It would be more about copying the batteries terminal structure, such that you could build products compatible with the battery or a battery compatible with the products. It snot about copying the battery, its about supporting interoperability. That's what is at risk here. Sixty seven different kinds of outlets, or arbitrarily expensive ones where the "design" itself is licesned, instead of the code.
I think this is a very important point. I haven't read all of the briefs in this case, or looked at the arguments presented at the hearing, so I don't know if Google's lawyers stressed this point, but they sure ought to.
I like this framing and think it’s entirely correct, but I don’t agree that it necessarily dooms the interoperability argument.
Google wasn’t trying to achieve compatibility with existing code (for which, you’re right, they’d have needed to take the whole set) but rather compatibility with existing developers. Arguably, that is still interoperability.