It's technically possible to do lots of things in BYOND but these things aren't always practical. 3D graphics require a lot of math that DM is much too slow to process. You also don't have access to the graphics hardware.
But you can't make a viable game out of it, nor is anyone playing that. I can make tons of pointless stuff with BYOND that aren't wireframe monkeys.
I don't think that was the point he was trying to make; if you do something like what he did, you're pushing BYOND's limits nonetheless, whether it isn't substantial on a hosted-server or not.