Does the "running technique" of Seiho players exist in real life?
I don't know this running technique, but I can tell you how important it is to swing your arms properly while running.

Have a Look here ->
LiveScience Arm Swinging.


  The scientists found that swinging the arms reduced energy costs by 3 percent compared with holding the hands behind the back, 9 percent compared with holding the arms across the chest, and 13 percent compared with holding the hands on top of the head.


If you have a look at professional runners, you will recognize how focused they move their arms. I can't tell if this special arm swinging is working, but there are surely different techniques to reduce your energy cost by swinging your arms.