It takes a lot of time, strength training, progressions and patience to get a strict muscle up. Some athletes are more than strong enough to do the strict muscle up, but they lack the technique to complete it.
Some athletes understand the technique but lack the strength. And then, there are the athletes who can do the kipping muscle up, but can not perform a strict one
Athletes are unique in their abilities. The road to achieving either strict or kipping muscle ups -safely and with good technique- takes time and a lot of repetition.
Philip has been participating in my gymnastics class for about a month. His athletic background in wrestling and his body type made it easier for him to grasp the technical aspect of the muscle up. Strength was not a problem for him. He did an outstanding job!