Is the Treasury Department selling the bonds or is the Federal Reserve?

Wasn't the action being taken in the article simply a cap on the amount of reinvested bonds? Doesn't that lead to a gradual decrease in purchases of mature bonds rather than a "fire sale"?

I'm not challenging your position, I am just seeing a terminology mismatch between your comment and the content of the article. I, a financial layperson, am likely not the intended audience of the article, which appears to be targeted toward economists or otherwise well-informed readers.