I can't reproduce what you say so I assume that you have disabled the password lock of Mac OS and because of the speed of your macbook it seems as if it doesn't

I can't reproduce what you say so I assume that you have disabled the password lock of Mac OS and because of the speed of your macbook it seems as if it doesn't go to sleep and then come back even though it does. When I do what you say I get confronted with the lock screen after things like music stopping and the mac going to sleep for a split second.