There's no such thing as a "natural" aspect ratio, because sitting with your eyes glued to a monitor isn't what we evolved to do.
Years of designing software have taught me one thing, which is that interfaces have to suit the task. When I'm writing or reading, I like a vertically oriented monitor. When I'm watching a movie, I like wide aspect ratio monitor. When I'm programming, I like a moderate aspect ratio landscape monitor, but very, very big. Bigger than I'd want to read a book on or watch a movie on.
So every monitor used for every kind of task is necessarily a compromise, but some monitors may be just the thing for a certain task. Maybe there's a task or mix of tasks where an 19" x 19" sqauare is a good compromise, or a single task where it's ideal. They seem to be pitching it at CAD users. I can see that. I've got my bridge drawings in a rectangular area on screen, but I still have another generous rectangular area for property sheets, tool palletes etc. When I'm working on my tower I arrange things into vertical rectangles.
Or this thing could be a nutty idea in search of a use. But there's probably one out there.