Twitch free packs

From the blog: "...watch 2 total hours of any Hearthstone stream on Twitch to get 1 Ashes of Outland card pack. Watch for 4 hours (consecutive or non-consecutive) to get another one!"

For me, that wording implies that the only requirement is to watch something that's under Hearthstone-category in Twitch so even streamers that aren't participating for this event would be an acceptable choice. I'd still play it safe and pick one of the streamers listed in the blog or just watch the main stream.