I've heard this from quite a few Instructors that started with PADI. When an Instructor gets more experienced they often want to progress from the paint-by-numbers philosophy.
It's not uncommon. The structure of the PADI system is good for new instructors - nearly all PADI instructors reach a crossroads.... some have an epiphany that enables them to make the PADI system work for them, others chose to crossover to another agency. Some just digging the ruts deeper and keep going around the same old track.