not really what you call proof
, if the ID video came after the leak, then yes that would be proof, but ID available before the leak, if it's fake, he could have used the ID to make it more believable, especialy that the ID was known for a long time from various videocardz leaks.
but still to me this performance is where a cutdown Vega should be, but certainly not the full chip, at least i hope so, because im really not that confident that AMD would deliver with Vega, i had a gut feeling that something went wrong with vega's developement, and my worry grow as time goes by.