FBI would be the primary agency investigating TSB leaks, so no need for a coordinated messaging campaign.

If the FBI believed that TSB was Russian intelligence, it is perhaps somewhat surprising that it's not mentioned in the Mueller report.

We also still don't know how Hal Martin was related to TSB, the timing of the messages sent from his twitter account to Kaspersky (who apparently reported him to the NSA!) does pretty directly tie him to the TSB.

The FBI would still need to coordinate with the NSA for an investigation and public declaration of findings, neither would be in the interest of the NSA to cooperate for.

And the Mueller report was specifically scoped down to not include anything outside of the 2016 presidential election. I don't know why you keep going back to that.