It’s not quite the same functionality. That’s what people are saying that the functionality is missing, and what @bravenel has provided to replace that.
The new smart lights does have the ability to set a rule to turn off after a period of inactivity on a motion sensor, but the options are only available to you if you also included in the same rule that you were going to turn on the light from that same motion sensor.
However, many people have use cases where they turn a light on for some other reason, perhaps just with a wall switch or a virtual switch controlled by Amazon echo, but then they want it to turn off after a period of inactivity. That’s what this community code provides.