Doesn't seem likely to me. If the attacker has password hashes then they would want to keep this attack quiet so that the buyer of the hashes would have time to

Doesn't seem likely to me. If the attacker has password hashes then they would want to keep this attack quiet so that the buyer of the hashes would have time to compute the passwords. If Twitch gets wind of this happening then a simple password reset would foil any efforts.