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^ I actually think that Eyeball illustrated that it's actually pretty straightforward. He needs an angle angle more like the one in the diagram above and a second flash to light up the face, and then I think it would look really close. And no, this doesn't explain the glasses but perhaps that's not DOF but more a function of imperfections in the glass or the incident angle of reflection being a bit too acute.
I actually tried to throw some light on the front of the subject with a reflector but it wasn't enough to be noticeable. I was losing the light and too tired to set up another flash but, yes, I think that would have done it. Honestly, I can totally imagine a roof-top set-up where this could be done pretty easy. Think about an observation deck with an open top but with glassed-in sides. Something like that would do it.
Difficult to be sure what method the photographer used. The online articles are not consistent. What is funny is that anyone seeing these images will think they are done in Photoshop anyway, so I'm not sure it matters.
Still, I thought the experiment was interesting and I think it demonstrates that reflections can be a powerful tool for wedding photographers. I was reminded of the beach house reflection photo that was posted a while back and the the one where the backlight projected a shadow of the couple onto glass between them and the camera. When the couple knows you did it "live", it probably has more of a "wow" factor when they see the print.