I noticed double click speed is also difficult for my grandparents who don’t have the same condition I do but they had no issues with older TouchID based phones. Double click-to-FaceID comes up quite frequently with use, enough to give my grandparents the impression that “this phone won’t work for me”. It’s a shame.
I’m strictly in the Apple ecosystem but was pretty surprised when I saw a friend’s Google phone with fingerprint based biometric authentication through the screen. Hope Apple develops something similar.