Actually, Cheyenne & Arapaho lane stitch also 'humps'. It must be a cultural/regional characteristic.
An excellent study on the terminology of this beading styale is presented in theis article by Joe Rosenthal (Joe frequently conducts bead & quill classes at the Carolina Indian Seminar that I recently attended with the ribboned veteran shirt). The History of the Term "Lazy Stitch"
He brings up that there is some that have called it 'hump stitch'.
<Per Nativetech.org> Until recently American anthropologists and beadworkers referred to 'lane' stitch as 'lazy' stitch (coined by William Orchard in 1920's), or derogatorily, 'lazy squaw stitch' (so-called by Benjamin Hunt in the 1950's). W. Ben Hunt wote a couple books on NA crafts & projects that addressed the capabilities and materials available to the post-WWII youth (in particular, the Boy Scouts) and hobbyist. His book, 'American Indian Beadwork' was co-authored by J.F. 'Buck' Burshears, who was the founder of the Boy Scout Troop in La Junta, Colorado that performs as the Koshare Indian Dancers - dance impressionists that travel nationwide.
I believe that lcp was referring to painting the stretched canvas that will be used in a beading project. The frame in my pictures with the Sioux Star is medium weight beige canvas painted with household latex. I recall the reasoning was the paint gave it strength & helped prevent fraying when cut-out. The edges are folded back under as it is sewn into the final project. The instructor that gave us the frames is mentioned in the last paragraph of Rosenthal's essay - Marshall Ellis. I may contact him & ask about the purpose & origination of painting the canvas...