I think the point is that the windows on the starboard side (our side) are more or less matching up perfectly with the ones on the port side - meaning that we can see right through. Quite difficult to time this right as well as being at the exact altitude necessary for them line up.
Also, you can see some silhouettes of individual passengers, which is kinda cool.
I took the picture from about 500 meters away. If you look closely, you can see that the windows at the front and back of the plane aren't lined up perfectly because perspective is a thing.
I happen to know a spot that lines up pretty well with planes landing on that particular runway. Then it's just a matter of spamming the shutter until one of the shots comes out like this.