I have the same MacBook Pro. This is a great question. I know exactly what you mean. You want to walk away expecting the Mac to dim the screen after a certain amount of time and then go to sleep after a certain amount of time has passed after activity has stopped.
The article for Setting Sleep and wake times doesn't explain it but there is no longer a control for setting a timer for sleeping after activity has stopped. It may be a relic of the past given power saving OS services. There is only a timer for turning off the display.
If I had to guess, Apple has decided the automatic power saving features are all that's needed. So the various services of the Mac will go into low power mode and if you think about it, if all the services are in low power mode, isn't that the same as sleep? Anyway, I've found it does sleep eventually. I just can't control it.
However there is a checkbox to force the Mac to NOT SLEEP automatically.
That's my guess.