Interesting. I viewed the NGAA as having a pretty strong hierarchy, but saw most of the innovation come from individual schools (from the experienced folks in them), rather than from further up in the hierarchy. Fine-tuning came from higher up, and innovation came from experienced students and individual instructors.Story time.
We had some gun BJJ black belts rock up to our no gi class. During drilling out purple belt was coaching them.
Then he found out they were gun black belts and apologised. The response was. "No that is good everyone has something to teach"
This is what fundamentally drives BJJs progression forwards faster than a style that has to wait for advancements to be filtered down from the beurocracy.
This is because more people are actively advancing the progression of the style. It is a basic numbers game.
I do think that a hierarchy can stifle some innovation - it's one of the reasons I haven't rejoined the NGAA, in spite of an invitation to do so. I prefer to have the freedom to do as I see fit with the curriculum.