The tweet's saying the govt isn't going after Tornado Cash. They've said they won't appeal the court decision. Roman Storm isn't free he's going to court because they're saying he knew his mixer laundered money so his case's continuing.
Unless there is proof from evidence like Roman's communications, I don't see how can they prove that he knew in advance that people were going to use Tornado Cash to launder money. While laundering is obviously a risk with any privacy protocol, that doesn't mean that its creation was intended for that.
I wonder if any bank executives have been under this much scrutiny for laundering, since banks (arguably) have much worse laundering statistics/affiliation with criminal activity are much higher than that of what all of the crypto ecosystem have involvement with.