It coud be that they are using roll paper, their description of:- "Papieranschlag in two schlitzen (oben und Links)" suggests, with my limited German, that the unit will have a maximum image size of 71x28cm and that there are two masks that slide out, one from the left, the other from the top.
I could be wrong, but it would seem that 30cm roll paper with 1cm of paper running in a gutter slide to keep it flat, would give you a top to bottom image of 28cm as a maximum. By using slide out masks, one from the left and one from the top, you can frame correctly.
I have used roll easels before and one that I used did have masks that slid out like a holland blind from one side that I can remember using. The idea is to use as little paper as possible on the long side, excess paper used on the short side is just waste anyway.
That said, roll easels generally are not moveable, well not much as they are usually pretty big mothers, plus they mostly have paper coming from one side (all I have used came from the left) then all exposed paper goes into a magazine on the right. After a point of time, either from the amount of paper used or the number of exposures done, the paper is slit, then rolled completely into the magazine which is then taken to the roller transport paper developer machine and either fed by hand, often B&W or by attachment, colour.
Interesting format as it sort of works out proportionally to my 35mm Horizon camera and would probably be better suited to 6x17 negatives than 6x12 negatives.
Whatever it turns out, if it's eventually built that is, it can only be good for us. I doubt though, if any private individual would require one. I myself have a negative mask made for my panoramic format 135 camera (Horizon).
For enlarging I made my own easel and use paper cut down from 12x16", with the waste strips being used for test enlargements. For smaller prints I use my Jobo easel which has various masking possibilities, one of which works out almost exactly to the Horizon format, 24mm by 56mm.
Mick.