In this role he is presiding over the senate. The question is not a question of law, you are correct that the leaker cum whistleblower has no right to anonymity, ID is not not protected (not a whistleblower), and would not be protected even if he was a whistleblower. 50 U.S. Code S: 3033 - Inspector General of the Intelligence Community
the Inspector General shall not disclose the identity of the employee without the consent of the employee, unless the Inspector General determines that such disclosure is unavoidable during the course of the investigation or the disclosure is made to an official of the Department of Justice responsible for determining whether a prosecution should be undertaken
The senate has decided to hide this highly relevant information from the public. Simple as that. No legal authority, just politics. The senate wants to keep you in the dark. Roberts, presiding over these proceedings, is following orders of the senate.
so this was voted on as part of McConnell/Schumer rules governing the trial?
Roberts wants nothing to do with this food fight