One of the two controversial "take backs" Seth had: https://www.twitch.tv/magic/clip/VenomousSolidBaconDansGame-LnIY9xnX9rDABQLR
Ken played Broodspinner off Cavern of Souls so while it was uncounterable, it was still targetable by a counter. Seth goes to sacrifice 2 treasure tokens to play It'll Quench Ya! but unwinds it himself, remembering out loud that Ken named Spider on his Cavern.
Not sure how I feel about it; watching it in the moment I felt like he cast that and can't take it back, but also Ken didn't call a judge and just went with it. His hands never left the treasures either. I think overall the "spirit of the game" would be that Seth was just thinking out loud and didn't fully commit to it, but a game like this should definitely require more precision.