This isn't quite right but I don't blame you, seems like few people really have this mapped out in their head. It either speaks poorly of the feature, the education around the feature, or both.
Rest doesn't just change the behavior in those situations you describe (raise to wake and sleep button). In fact basically any interaction with the lock screen (or peripheral functions of it) after waking the phone mean you then have to press the button, not just rest. Try waking it and scrolling notifications, sliding to camera or sliding to widgets. After that you must press the button to get to the home screen.
The only reason I don't tell people to turn on the rest finger option is because I expect we'll see more and more widgets and rich notifications that require you to unlock to perform some interactions. People who have that (accessibility) feature on will, instead of just unlocking and interacting with the widget/notification, be thrown to the home screen. If nothing comes of that, and no developer uses that authentication, then the ability to unlock on the lock screen is basically there for nothing. Only time will tell I guess.