I was in a bar with a girl I'd been dating. She bumped into a guy she'd had a long-time affair with sitting at the bar. He was a successful artist (I later saw some of his work at a gallery in town), nice-looking, dark curly hair, Italian type, shirt open revealing a hairy chest. I was shocked when he slipped off the bar stool - he was barely five foot - if that! One of the shortest guys I've seen not actually a midget or dwarf.
Later on, I must have made some comment about his height, for she replied, with a mischievous twinkle in her eye, that you can't tell a book by it's cover - she indicated this guy who barely came up to my navel was super mega-hung! That definitely knocked me off my high horse, since, although 6'3", I'm hung like a chipmunk. I ran into him a while later and had to constantly restrain myself from checking out his crotch!
So no, there are short guys with big cocks. One of the better-hung (verified) guys on the site (sadly, no longer active) publicly listed himself as 5'7" but confided to me that he was actually only 5'5". As the lady said, you can't tell a book by its cover.