Rimless toilets, and "not suitable for installation with flush valves"
So called V&amp;B. The guy "simplified" the description, and stated that it's kind of been lost in translation; a lot of links on the English site even go to the German one. What not suitable for installation with flush valves means is that a cistern must be used that has a push button flush. He mentioned requiring high pressure, but that other flushing mechanisms using levers, direct mains, etc. will not work. 

I mentioned our cistern does 3 / 6L for dual flush, and he mentioned that the installer can dial down the full flush to 4.5L, as that's all the Direct Flush systems need. A 6L shouldn't cause an issue as the V&amp;B rimless flushes have a flat "rim" (well, they call it a ledge) that prevents splashing, and since water is released along the sides of the rim, extra water would merely be waste. Still recommended dialing it down to prevent water wastage.