Cross-Stitching From The Back - The Miao Way

In her fascinating book, Miao Embroidery from South West China, Ruth Smith documents with images the practice of Miao embroiderers to work their cross-stitch from the reverse of the fabric. They say the stitchers are able to work very deftly and quickly.

I am a little puzzled as to why one should work from the reverse of the fabric, and maybe you have some thoughts on what the benefits might be. Would it be so that the fabric doesn't have to be flipped for starting and finishing off?

And here you can see the diagram of the working.