Yes, I recently noticed those – and I do like the design.
Evidently, that system has become a hit, since you can buy natural stones for it from other sources as well: Naturstein Scheiben für Rollschleifer, Schleifstein Deluxe- Original Belgischer Brocken online kaufen
My goal has been to master manual sharpening using Japanese waterstones. Unfortunately, my hands are not sufficiently steady to maintain a steady angle :-((( — so I have to make do with some kind of “guided system”. The Horl looks promising, as does a Russian engineer’s wet (perhaps whet in this context) dream, the Tsprof — but the latter is quite expensive.