Actually no, what Bruce learned was Wing Chun, and I believe the only form he finished was Siu Nim Tao, some Muk Yan Jong and possibly some work on Chum Kiu. And although there is an argument that Wing Chun is an internal art, by definition it is not. However I tend to put it in the same category of internal you find Xingyiquan. But still, by most standards of an Internal Chinese Martial art it is not internal (but then Chen Fa Ke never called his Chen style internal either) The rest of what went into JKD came from various other sources, none of which would be thought of as internal; Boxing, fencing, etc. So I believe you are incorrect with that statement.