"True Cross" and "Reserve Cross". Warping frame with 4 pegs.

I was browsing the web for information on Japanese weaving and looms when I came across some images from the Kawashima Textile School in Japan. I noticed they wind their warps using a horizontal warping frame that has 4 end pegs.

I found the website of a weaving supply shop based in Kyoto that sells a similarly designed warping frame, and the description briefly states that the 4 pegs allow for a "true cross" and "reserve cross" to be formed. Here's the link and some images of the frame and cross formation:

http://english.inagakikiryou.com/s_seikeidai.html

I've seen North American warping frames that are designed with 4 end pegs, however I haven't found any information about this particular method of forming a cross. Is anyone here familiar with this technique of forming a "true cross" and "reserve cross" while winding a warp and can explain it's purpose/advantages?

I would've tried to contact the Japanese weaving shop directly, however it seems there is no direct way to contact them...