It must hurt to be greek and see that credits page, haha!
Actually, the reason for that might be quite simple; back in the day it was thought that having a big D meant you were someone undesirable, nonintellectual, and gave into your baser instincts - this is why old statues of men always had fairly small Ds and why barbaric people were thought to have big Ds (which is where the reputation for black men and their johnsons came from, that old barbarian stigma).
So it wouldn't be surprising if Greek men just selectively bred themselves into having smaller members, thinking themselves intellectuals.
All this said though, I could've sworn Japan were the... most
'intellectual', but I guess the Greeks take the cake.