I interpret that statement to mean that he placed the two phones back-to-front, flat against each other, and slid the one toward him over an inch or so to give its camera a clear view. This would allow him to hold them comfortably and get nearly identical views of the scene.
The image of him in the mirror is pretty difficult to see clearly, but certainly consistent with that. You would only be able to see a half-inch or so of the second phone poking out from one side, and there's no way I could pick that out in that video.
Ah... I didn't think about it that way. I thought they would stacked vertically but I see how your suggestion of them being placed back-to-front with a slight offset so as to give each camera a clear view would be easier to accomplish/hold and would give nearly identical views of the scene. If that is the case, then more than likely the video is genuine and I retract my doubts.