See also the great game Race for the Galaxy, where my friend Wei-Hwa Huang laid out the cards in bizarre symbols I'm sure he completely understood. This does not mean that I do. That said, I have not asked him whether he understands Gloria Mundi's symbols.
This example is especially salient if, say, Wei-Hwa has kicked your butt at Race for the Galaxy. It tells you why you wouldn't bother asking if Wei-Hwa understands your game's symbols (since he does, of course, even if he had to reverse-engineer their meaning by learning everything else about the game first).