People are brainwashed by their prior experience: they have seen so many puzzles with specific assumptions that they assume them to exist here, as well. The qu

People are brainwashed by their prior experience: they have seen so many puzzles with specific assumptions that they assume them to exist here, as well. The quasi-pyramid is impossible if you assume that there are no hidden nodes and edges. That assumption is not an explicit requirement, so you can posit any number of nodes and edges that are hidden from the specific perspective of the drawing -- it could be as crenellated as the interior of an English muffin.