Yes, there are exceptions. But by and large, taller players are better in the air. Tim Cahill is average height and an exceptional header. Aguero is a pretty good one for his height. But Dave is damn near useless with the outside of his head. No surprise there, the inside of his head is magical.
The strike radius for a taller player is just greater. Yes, you have your exceptional short leapers. And your Crocodile neck tall guys (Yaya being a good example). But by and large taller players score more goals with their head.
More of the rule though. There are plenty of tall players not being very good in the air