Nitter is a third-party Twitter client. Think a version of the web experience that consumes the public fundamentally public view of Twitter. No API tokens involved.
https://www.inverse.com/input/tech/nitter-is-a-new-front-end...
So... Trying to say that Nitter has a CSAM problem means not that the Nitter instance is hosting CSAM, but that Twitter itself is hosting CSAM.
Now if you have a higher signal to noise ratio at finding CSAM through the Nitter client, that's just because you knew where the content was on twitter and accessed it there. RTFA'ing the article reveals that someone reported the Nitter instance, not realizing they should have been reporting Twitter instead, and the apparently unsupervised automated pipeline that leads from some technically illeterate concerned citizen in the U.K. through an internet non-profit IWF, to the German Federal Authorities, to a German VPS (Netcup), led to the sudpension of the client instance with a demand to remove the content in question, which again, is hosted by Twitter.
So... Yes. These CSAM reporting pipelines are basically site takedown shotguns that are apparently so minimally supervised, it is easier to just give up trying to host than to get someone to actually look into the matter.
This is actually one of my biggest concerns with how we handle CSAM. I acknowledge it is horrible, and I acknowledge it is a problem. However, in it's current form, it is a strongly weaponizable form of censorship, with little recourse to be found, and so many people in the bloody loop, but no one whose job it is to be publicly accountable for said loop and it's actions that someone wrongfully on the receiving end of one of these things can push back through.