People who can go fairly height with out much preload are lucky with genetics.
Pair up that with good technique and the end result will be better.
Of course there are always some freaks out there.
Practice does not make perfect, only perfect practice does. If your using a bad technique and practicing that over and over it's going to make it difficult to loose those 'bad habits'
Using a flat tyre is a good example, you don't eat to relie on the tyre to get you up there, will only get you so high and if rimming out you are losing force generated