That subwoofer placement strategy is in the manuals for all the LFM subs. It is based on the idea that all reflections are symmetric (which they are!). If your sub is in position A and you are in position B, it will sound the same as if you put the sub in position B and you listen in position A.

Taking advantage of symmetries was the most important thing in high level physics classes.... now someone is putting it to good audio use!