Alternatively, do you have "easy screen turn on" set to ON in Settings -> Accessibility -> Dexterity and Interaction? That allows screen wakeup with a hand wave over proximity sensor, but this is normally turned off so you probably would have remembered if you changed it to on.
So true. I almost forgot about that setting which will basically keep your phone on constantly if you're carrying it.Proximity sensor would unlock if enabled on your body.
It's called Smart Lock, but, it should be called Smart Unlock.
Settings, Lock screen, Secure Lock Settings, Secure Lock Time, make your selection here.
You can disable this by going into Settings -> Navigation bar -> Hard Press Home Button disable this setting. It seems that if this is enabled it overrides the "unlock with home button" even if you have the "unlock with home button" disabled. I was getting super annoyed with my phone continually being unlocked and finally figured it out. Hope this helps you!