I still haven’t found a practical use for it.
This morning, my watch alarm went off. Tried to double-tap to turn it off. Since my watch is still in Sleep Focus, the screen doesn’t turn on, so the double tap doesn’t register. I had to press the crown to turn the screen on, and then the double tap worked.
During a workout, a double-tap to pause would be nice. But no actions register during a workout.
It’s gimmicky.
It’s new, it will evolve with updates.