Comey was asked about that in the hearings today. Comey said that he asked the DOJ if he could reveal the investigation and the DOJ said, yes you can. As Rush said today, the Trump admin runs the DOJ and apparently the Trump admin wants everything known and in the open.
No I disagree with your interpretation. He asked for permission to reveal the investigation and the Department of Justice, which would not be Sessions now but would be the deputy, probably did not feel comfortable to say no.