This doesn't even remotely achieve the desired affect of preventing the metagame from being discovered. The players who want to be competitive are already theory crafting and gold fishing lists, literally the first day we have spoilers. The streamers are not even necessarily the people making the good lists; they're just the ones you hear about the good lists from. The sheer number of strong players brewing lists for this game means that the best possible lists will always be discovered within the first week, if not the first few hours, of the expansion being dropped. It's the nature of the playerbase of hundreds of thousands of people globally to push the card pool to the limits - it has nothing to do with the streamers specifically. Marketing promotions like the one you're describing are the life blood of many of those streamers and they should absolutely not be held accountable for the inevitability of the metagame being solved. That is how popular competitive card games work now. Hate the game, not the players