You have a fair point. Not gonna deny anything that you said.
However, this will most probably be the last home-buttoned iPhone your father-in-law will own. As the rumour mills suggest that the next generation of the iPhone SE will come with a FaceID and will have a larger XR-like design.
If that’s true, people sceptical about the ‘identity threat’ shall have no option but to wait until Apple releases a phone that has Touch ID in the side button, just like the newer iPad Airs.