I wonder if a magsafe secured, size agnostic version could be made. Less locked in but easier to split across pockets and possibly works for more than one model.
This certainly must have been an option they explored. Without a case secured to the body of the phone, pushing the keyboard buttons would probably pop off the magsafe connection. There's a lot of leverage on those clicks.
But also.... no, I don't think I need/want this. But a cool design exercise.