its based on the theory of even body proportions, by proportion your foot is supposed to be the same length as your forearm, hand as big as your penis... but some times beople have odd growth spurts, hormone issues ect. and some times some folks just strait up ain't made that way.
its a likelyhood i guess but nothing is 100%
That's true for me too.
it's not true people, maybe for some people but that's what makes the human body so "amazing" they are all unique and one of a kind.
There's another myth that says your penis head is as wide as the space between your pointing finger and your thumb, that one is true for me.
That would be hard to tell, how are your finger and thumb positioned? If I'm making an L my head should be 3 inches across!