GAPP is manufacturer-led accreditation for licensed waterproofers and trade professionals. It is not an RTO qualification and it is not trying to be. What you get is current standards, verified detailing, a manufacturer behind your application, and a card that tells a builder you do it properly.
Trainers have twenty-plus years on the tools. Classes are capped, so you are on the tools and asking about your own jobs, not sitting in a lecture.