Both can be true.
Twitch is run by the clinically insane. We can all agree on that. We can also agree that they'll only act on people they hate because as we've constantly seen when it comes to partisanship people will turn a blind eye to their fellows while crucifying their enemies. Never mind their behaviors are the same or worse. The only reason people would know about these messages in particular is because they were actively looking for something. It happened in 2017 and they didn't do anything until 2020. If they had a team of people combing through their creators' DMs - because let's be honest, the average userbase would be way too large for any human team to accomplish - then they would have done something in 2017.
That said your DMs are public to the company. However, if they have a team they hire to go through DMs then they would have already acted on it a long time ago. If they didn't, then that's making Twitch look even worse than they already do. Granted, not as bad as Doc, but if they sat on this for three years then that would certainly bring them up to his level... or down.