You are not shaving off a 6k edge, it is a 30k, .50um Chrome Oxide edge. With paste you can go much quicker and higher, with Nano grits.

The goal of bevel setting is not to produce a shaving edge, it is to,1) flatten the bevels, 2) set them at the correct angle and, 3)get them to meet at the edge. You can refine a 1k edge by altering pressure and technique, trailing or leading. But No-one will be shaving off a 1k edge, except those that shave with EDC knives.

The difference between edge trailing and edge leading is, with trailing you produce a burr and break it off, creating a microscopic ragged edge by stropping, leading you cut off the burr with each stroke and produce a straighter, stronger edge. Ragged edges work well for knives, tools and axes, with razors you also must consider the skin the bevel and edge ride on, not just the sharpness of cutting edge.

For hundreds of years guys have shaved very well, off natural stones and barber hones probably in the 6-8k range. Blue slate stones run the gamut from slate pavers to fine finisher like Vosgienne and Salmen finishing stones.

Natural stones are natural, the composition or each stone and grit are unknown. Some can finish. A 12k Naniwia can do it all from bevel set, chip removal to finish. Check out this post, (12K Super Stone Chip Removal/Bevel Set). If you want a one stone solution, but why?

Also, a lot of deep vertical scratches on your pre-honed razor bevel, and most probably chipping your edge, your strop needs cleaning or replacement. Improper stropping and grit on leather strops do much more edge damage than shaving. A properly honed edge, properly stropped will last a very long time. Stropping is very under rated.