I like the variety in Predator heights.
Also Predators who grew up on planets with lower gravity or in space, would have less force pushing down on them as they grow, so they'd be taller than is average for their species.
I imagine the big ones like the 9 feet tall or 10 feet tall ones would hunt on planets with huge environments, like ginormous trees and massive prey rather than Earth which would be preferred by the shorter Yautja for its smaller environment.
Humans that grow up on Mars would be taller than those who grew up on Earth.