I too believe that the reason GJ did not grasp the theroies of his 7 masters is because of their own inabilities to teach correctly. GJ was able to learn QZ's internal energy for just 2 years and achieved results higher than most of the QZ disiples can, master HL18Z in a very short time, understand the theory of the dipper formation in a very short amount of time, immitate 1YZ just by seeing it, etc. Other than GJ being slow at other things, there are no indication that he is slow on martial arts also.