Try telling that to my 20mo DS3. He literally takes MY long hair and lays it over his head and says "mine want long hair".
Unfortunately I am currently refusing to buy my toddler a syrup, and his hair is stubbornly refusing to grow as quickly or as long as he himself would like it.
He has gorgeous red-gold hair, and is most obviously expressing a preference to have it longer.
DS1 has one of those stupid Justin Bieber haircuts, and in fact has preferred longer hair for as long as I can remember.
DS2 has quite close cropped hair, again because that's how HE has always preferred it.
DS3 I can imagine is going to want long straggly surfer type hair, from what I can see - even to the extent that he points out styles he likes on other DC's and tells me "my want mine hair long".
Each to their own, all 3 of my DS's have had very strong opinions on their hair from toddler age, and it's their head, not mine.
DD on the other hand, couldn't have given a shiny shit what her hair was like until she turned 14 years old!