nobody does "the" original yoga.

Its history is long, confusing, arduous and full of in-fighting. (I don't have much of a dog in those fights). If you're interesting, I found a lot of value of Mark Singleton's Yoga Body.

Just like Englishmen of a couple of hundred years ago, while nominally speaking "English", wouldn't understand us conversing today, yogis of hundreds or thousands of years ago would look at our practice and their practice as entirely distinct things.

so yeah, vinyasa (or hatha or ashtanga or whatever version we have done in the west in the last 150 years) has almost nothing to do with the yoga practice of ancient India (apart from emphasis on breath, body/soul, some postures, and spiritual aim).