You can’t predict how people would choose to secure their phones.
Having TouchID as an option has ZERO affect on how YOU secure YOUR device.
One example that solves your concern: During setup, ask for FaceID first, then passcode, then ask if they wan to setup ToucID. Hell, if they wanted to hide it, force users to go into settings later to set up TouchID. This way people have to already know about TouchID or discover it in settings. Setting up TouchID wouldn’t shut down FaceID. Authentication would be TouchID+FaceID. I can imagine allowing only TouchID, say if you break the front cameras.
I’m just spitting **** out of nowhere. I don’t even need to bother trying to justify a personal preference.
It’s baffling that people are so against the idea of behind-the-screen TouchID as an option. It wouldn’t affect you at all. Why is it so concerning how other people secure their devices? Should everyone give up on Android because it’s too insecure to use?