I've had the camera app in the same position on my home screen for years and even now I'll still unlock my phone, swipe up then tap the app rather than just long-press the camera icon on the lock screen. Muscle memory.
There are no buttons on the iPhone 11 that match up with the camera on the case. Our first guess was some kind of wireless transmission to the phone, but then we saw our patient’s X-rays. It turns out there’s a little circuit board inside the case, which has a thin, flexible circuit running out to connect to the photo button. That circuit board connects the camera button to the phone through the Lightning port “chin” at the bottom of the case. Not totally unexpected, but interesting to see how much hardware design goes into adding just one thing to a battery case.