For the most part, the US government is allowed to ask anyone to voluntarily remove anything (a few limits such as those set by the establishment clause notwithstanding). That's what happened here.
Or are they doing it under duress?
Of course it's the latter.
The US gov. has been threatening to take down social media companies for years. Do you think Twitter really wanted to upset them now?
It's like when people "voluntarily" do things that cops ask during traffic stops that are beyond what's necessary by law. It's not that people want, they are just scared and don't want to get in trouble.
Yes? When the CDC says "we recommend you get vaccinated against the flu", and you get vaccinated, you're acting voluntarily, despite the government recommendation.
Also, the guidelines ask you not to write comments like that.
It didn’t seem that the FBI were going into detail on any cases. I wondered if some were likely to be considered concerted foreign interference that they’d unearthed and policing that was within their remit. I assume there’s some overlap between Twitter’s ToS re misinformation and the FBI’s assessment, if that makes sense.