well i mean because the wiki page he linked to shows a penrose triangle, square, pentagon, and other -gons that are two dimensional shapes.
however, when you draw something penrose, you draw the edges of the 2d shape with three dimensional "lines".
basically
penrose + triangle = 3d shape + 2d shape
while
penrose + dodecahedron = 3d shape + 3d shape
so i just sort of assumed he wouldn't mean a dodecahedron because that's weird
yet you did it
so uh
nice