Twitch is a dangerous website, the extension probably won't be back. They could still easily target you at any time and you are just lucky they are sending ads. After some time of using the extension twitch will react and become even more toxic.
Twitch even has a network sniffer in its source code (among other things), its so much worse than just ads, some of these experiments are basically malware/pup that no-one would install on their device willingly, these instances aren't just left over code from some library they are deliberately crafted experiments that are present in the active code path.
I mean they can watch and monitor your activity on their website, and are probably partnered with many other websites to collate data on your interests and beliefs to feed into a chunky advertising algorithm sooooo...
We all know that to a degree, but do you really think they're in collusion with the US government to jail anyone who mentions it?
I also don't think the dude gave anywhere near enough information to explain why search engines and browsers should be blocking access to Twitch. They made a lot of claims, but no proof.
Yeah. Just to clarify, I didn't mean to try to validate conspiracy theories like these and wasn't suggesting that this guy is right, but that it's wrong to ignore the large amount of data that closed source applications oftentimes do collect on you.