I think you're getting confused here. There is no opting everyone in by default for location on iOS. They have to explicitly opt themselves in, if they want to

I think you're getting confused here. There is no opting everyone in by default for location on iOS. They have to explicitly opt themselves in, if they want to. Otherwise they are opted out by default. This goes for all apps and is enforced by Apple in order to maintain a good experience for the user.