I think the SA guys call it the "deadman" position, as it makes iit harder to breathe,.....
I have tried it, and it is not for everyone. I think it has a place in one's repertoire when adapting for difficult and varied elevation. It does give a much steadier hold,...........when all goes well.
That said it isn't the be all and end all of sitting position, just one variation.
Variation from all around the globe is throwing up some interesting styles, isn't it!