Tim Zowada's web site has some great 200X photomicrographs of various stone surfaces including the Chinese 12K. It's uniformity compares modestly well to the eschers.

Zowada Custom Knives - Stone Surfaces

I realize this is not the ultimate answer because there is no comparison of various stones ability to form a swarf with a given number of strokes. My guess is the Chinese 12K is harder and more resistant to
"surrendering" it's grit than most other stones, hence the need for so many strokes to polish a blade.

Don