Prosecutors never start off with mail fraud or its equivalent. It is always piled on at the end of other charges.
In addition, Comey’s memo leak led to the appointment of Mueller. Had Comey been indicted today, the media would easily convince their base that Trump was simply taking out revenge.
NPR this morning didn’t even mention the non-indictment. That is how worried they are.
Solomon's source specifically said that the decision not to prosecute on the two referrals was a final decision. There would be no charges on those two matters at the "end".
Question Solomon's unnamed source, that's fine.
I'm just pointing out that your above scenario doesn't agree with Solomon's source.