It's basically color tinted dip. You can get a similar effect mixing gloss coat and inks. The big trick is avoiding tide marks. If they've nailed keeping the flow consistant it's a big win.
Think of it like the Army Painter tone line. When you apply Strong Tone, it tends to roll off the high spots, and settle in the recesses. This looks like it has more pigment/dye in the medium, so it tints those high spots more. As the medium attempts to self level, more will settle it the deepest areas. It will be interesting to see how well it levels. I imagine that a zenthal preshaded mini in greyscale would work well with some of the colors.
I'll pick up a few to try them.