You assume right. The FBI knew what the dossier was, where it came from, and had no desire to expose it.
What I am interested in is the exact nature of the comments he lifted, because I suspect the characterization as “random” is a smokescreen. I bet that Simpson, Nellie Ohr, or others in cahoots told Steele where to look (if he even really did)and quite possibly had posted the dirt on iReports in the first place. I tried Washington Examiner, and their “Archive” link took me to some sort of product marketing scam.
It’s hard to find clear info, but the appearance at other sources is that the iReports material was Steele’s basis for accusing Webzilla and other platforms owned by the plaintiff, of fielding Russian bot farms, and anti-DNC computer attacks, etc. Very odd if that was on someone’s mind to post it in 2009.