My understanding is that this approach would not work.
If I have it right, the idea is to grind off all the sharp points of the abrasive grains on the face of the stones. That way they will no longer remove metal by 'stoning' or abrasion.
However, the edges of the now ground flat grains are now sharp. The gaps between the grains are now crucial to the flat stones' function: anything sticking up from an otherwise flat surface will 'fall' or protrude into the gaps and will get sheared off by the edges of the grains.
To make use of this property, the stones need to ALSO be dead flat.
To achieve both at the same time, a surface grinder is used with a fairly fine diamond grinding wheel. It needs to be fine so as not to rip out any grains, but grind them down.
I've done that as an experiment with a few low-cost bench stones. I found the bonding resin or medium of the stones needs to pretty tough. Many stones have their grains bound by fairly soft and weak bonding. I guess that's a good idea if you want to expose new and sharp grains for stoning things. For this purpose, that's the exact opposite of the properties we want for flat stones.
A couple of very cheap stones I found in local hardware stores had very hard bonding and sure enough, they were crap at sharpening tools. Even using their coarse sides, they would quickly stop removing metal and just polish or burnish metal.
Once I ground them on the surface grinder, they behaved perfectly as flat stones.
I've made a few pairs of them for friends and myself now. They do exactly what Robin described and demonstrated in his YouTube videos.
Cheers,
Joe