Excellent images in that document, and definitley a good read. The pictures lend to my original thoughts that a 4K would scratch up a nice 8K finish. However the edge required to best cut hairs in the facial enviorment may include the 4K groves. As we are not just cutting hairs, but also scraping away some skin (hopefully not too much) in a soapy medium. I guess there are a few factors to consider that may also affect the performance of an edge.
I may be wrong but will too sharp of an edge lend to razor burn? Or is that due to technique, like too much pressure or too steep of a shaving angle?

Emil