Hi Bill, well I'm not Ron of course (though I did stay at a Holiday Inn Express last night..), but I would have to suggest that thickness shouldn't be governed by its spectral sensitivity. One contributing factor to EK Panchro-Matrix being thicker than ortho might be the use of a heavier extinction dye/pigment. If there's a lot of carbon black(?) in there, that could contribute to the thickness.
It seems to me that once it's etched it shouldn't matter whether it started out as panchro or ortho, because having a thin relief is helpful in getting really good flush contact with the matrix & transfer paper.
I'd have to think that investigating PVA's dye imbibition properties would be paramount to coating thickness at this stage. But, whenever I say something like this I end up eating crow when a few more posts come down the line.
FWIW, the Polaroid Vectograph process relied on imbibing dyes to a polyvinyl-alcohol surface, so it will accept dye which is cheery news.