Hi! I've been to France many times and many of my closest friends are French and yes, I do believe there is a quintessential French style.
Only, I don't think it's so much about the clothes.
It starts in the mind, and like Lacroix says in that article, manifest in the gestures and the attitude. And the clothes ONLY insofar as they are extra "tools" to help you express that spirit inside you. I believe one can still exude the same chic completely nude. And like Elbaz says, to me, whoever has that quality will exude that style, whether French or not.
What exactly is that "aura" that shines through in French style? It's a difficult question, but I do think it comes from *knowing* you are a sensual, chic, and seductive being, exactly as you are and without having to change yourself--hence the minimal makeup, natural-styled (but well-groomed) hair/nails and elegant posture, nonchalant shrugs and challenging glance. Different from just "confidence", I think this is the quality that makes me do a double take when I see a woman with no makeup on, flat sandals and slouchy no-name clothes, but simply gliding down the street. I think this is why French women are so often mesmerizing even (and often all the more) with no makeup, dark circles under their puffy eyes, and messy hair. And I suspect it's not unrelated to France being a culture where maturity and intelligence are seen as seductive in women, as opposed to mere youth and "flawless" beauty.
Lastly, about the clothes; it's often true that they own relatively few items that they are proud to wear repeatedly for years, even generations. This is simply because they know what suits and fits them, choose quality, customize, and put thought to coordination and styling but not too much thought to trends...
Phew that was LOoooong!!