As a historical matter, you are probably correct. I would only add that we know Bruce Lee was something of a Taoist, and Taoism is the basis of much of JKD. Therefore I can't be certain which came first: the philosophy or the martial art. I do know they developed together after whichever came first.
This is an open question, one that Dan Inosanto and others that knew BL might be able to answer.
Probably it doesn't matter too much. After all, his whole intent was growth of personal expression. He probably would love that we are even having this debate.
I also agree with you that the martial art needs to be learned first before one branches out to other things, otherwise one's efforts become unfocused and the result of happenstance.
To go further with the Michael Jordan metaphor, he might have been even more fantastic had his mental training been molded by JKD instruction. We'll never know.
