This is an excellent question.
I have been studying for almost three years now at a school that we picked out of the phone book for my daughter. The school teaches 'Ed Parker American Kenpo'. When I started, the studio owner had a 4th degree black belt (currently a 5th). He studies with Mr. Planas. So, I believe that I am learning material from a Parker - Planas lineage, if you will.
Then I go and attend the Sunday seminars are the Internationals this year, and have a short class with Mr. Trejo, Mr. Gilbert, et al. The material I learn in these seminars is VASTLY different from what I have learned.
It makes you wonder how something as seemingly basic as a 'Twist Stance' can be interpreted and taught so differently.
At this point, I don't have enough of an understanding of the system to know what is right and what is wrong. I need to continue my studies with my current instructor, at least through the Black Belt level. He often adds the 'WHY' we do things to the material presented. And, I need to not attend seminars.
Eventually, I hope to be able to spend some time with Mr. Planas one-on-one, and further my understanding directly from him. Further, once I understand the material as presented through Mr. Planas, I can begin to further evaluate other material as presented as American Kenpo.
There are two sayings I try to remember;
"What is useful, and what is useless, will make itself known through time, practice and logic."
"He who knows HOW will be the student, and He who knows WHY will be the teacher."
Because of the ego's and the business plans, I do not think any organization will ever be able to re-unite the Kenpo community.
Peace - Mike