Me and a bunch of other people didn’t receive the guaranteed 2x SoU drops and the reason seems to be that if you were watching the stream right before it went “live” when it was running reruns you had to refresh the page in order to be eligable for the drops (based on a Reddit comment: https://www.reddit.com/r/hearthstone/comments/crkhoi/twitch_rewards/). If this is true it should have been stated beforehand because this has made people miss their guaranteed packs (based on various Reddit threads and Hearthpwn comments).
Here’s a few sources where people have said they’ve fullfilled all the requirements including the 6+ hours of watchtime without receiving any Uldum packs.
https://www.hearthpwn.com/news/6891-masters-tour-seoul-free-packs-from-twitch
https://www.hearthpwn.com/news/6899-masters-tour-seoul-final-standings-and-decklists
https://www.reddit.com/r/hearthstone/comments/crjie6/i_did_not_receive_the_twitch_packs_whats_going_on/
https://www.reddit.com/r/hearthstone/comments/cqzc7q/twitch_drops_enabled_masters_tour_seoul/?sort=new