Pretty sure it is. I am the bloke standing next to him in the DMP. The picture doesn't show the wrist hinge which is forward of the knee therefore if he rotates his hand it will fall clear. Don't think there is a rule stating forearm orientation is there?
Rick Ardern super low mounts ISP MK3 pellet launching platforms and Sightron 10 x 42mm telescopic sights.
Because it is not about how, but how many.