If you’re going to walk down the up escalator, you have to walk faster than the stairs are moving. Otherwise, you won’t go anywhere. (Trust me on this, I took approximately three physics classes in college before dropping the course in favor of a semester of learning underwater basket weaving.) If you walk at the same pace as the escalator, you’ll find yourself trapped on a never-ending IRL StairMaster. And possibly the subject of a viral video, like this anonymous couple making the internet rounds today.
Alternatively, maybe the pair was just looking to meet their step counts for the day and tone their calves.