Seems like the K-frame must have some impracticality being I can't recall ever seeing new lines ever using that spec.

Makes sense. I reckon H-frames are also much simpler to erect as well.

I wonder if wood handles tension better than compression? If you look at the H-frame, almost all the line forces are pulling down on the main arm, and the braces up above help support the arm against that tension. On the K-frame, the two outer phases are pushing down against the outer braces, and there have to be some complex forces acting on the center of the 'K'.