How is the Smart Garage Door Opener different from using a momentary switch with a relay?

Is the Garage Door Opener similar to a momentary switch?

The Smart Garage Door Opener works similarly. The Smart Garage Door Opener product uses a relay to trigger the door to open and close. It also has an optical sensor to see if the door is open without needing a wired contact sensor. It also supports a wired contact sensor.

In short -- similar technology, just a more streamlined purpose-built product. In SmartThings, it shows up as a Garage Door entity instead of a separate device for the switch and sensor.