I got my bottle of Indian OS in the mail this morning, so I have been doing as scientific an experiment as is in my power.
I put vintage OS on the back of one hand, and Indian OS on the back of the other, and I have been sniffing them over the course of the day as they fade. There was a bit of difference when they first went on, the Indian had a more alcohol note, for want of a better term. But as they settled down they are indeed almost the same. And when I say almost, not different enough that I would notice or care about if they were not side by side. To my nose they are basically the same thing.