I can't judge about the reason of such proportions in the VMs, but the author of You are not allowed to view links. Register or Login to view. writes that sometimes disproportions of bodies were intentional "to focus attention on one body part (often the head)..."
One more idea:
as stars, constellations and planets (astrology on the whole) must influence on a newborn in a hour of his birth and over whole his life, this symbolism could be explained in such way.
One more idea:
as stars, constellations and planets (astrology on the whole) must influence on a newborn in a hour of his birth and over whole his life, this symbolism could be explained in such way.