To be honest, I have never ever considered YSL niche. In France their fragrances Y etc, have always been available in their version of chemists. They have destroyed their classics like Y, Rive Gauche and of course Opium.
They are more famous for their make up range which is classed as high end, nothing more. You say YSL to any woman and the first words will be Touche Elcat. A friend is a manager of a YSL counter and when chatting with her if I see someone approaching the counter. I just repeat, Touche Elcat over and over.