Cotulla is a very trusted developer and would most likely not release a fake video, he is 100% legit in the WM deving community. He brought linux and further pushed Android to the HTC HD2, along with tons of other things.
Cotulla said the following thing on twitter:
“Remember this is just DFT team tests, please never ask about release date and etc. Please don’t annoy with questions…Future will show all.”