The SmartExtension SDK was first developed for the SmartWatch and Smart Wireless Headset pro, but was also intended to be used for future products. Thus, we took a broad perspective on the API and its methods, to be able to be as future proof as possible.
So regarding the LED, as you say, it does not exist on the SmartWatch and the code is not there for the LED on the phone either, but could be used for any future products that might come in the future.