It's the combination of vertical but still staggered (keys placed in diagonal columns). Sordna (I think) has tried a vertical arrangement, but with a matrix layout (keys arranged in a grid north, south, east, west) and found it to be much better.
The yogitype has the staggered layout on the right, but matrix on the left.
You'd be better off asking the question about the supports in the ergonomics sub forum to be honest.