Steve
Mostly Harmless
It hurts that you aren't sure whether it was a joke....Not sure if this was intended to be a joke. Any such list containing 753 styles would definitely be bogus. It's possible that Lee might have come across the names of that many styles, but I wouldn't bet on it.
I can't find my copy of Paul Vunak's book on JKD. If I recall correctly, he lists 17 different styles that Lee drew upon for JKD. I think only a few of them were ones where he had any actual official training in the sense of having taken classes in the art. For others he might have exchanged information with friends who studied the arts in question. For others he just read books or watched video and stole an idea or two.