Good point.
1. There is no "whistleblower."
2. There is a group of perhaps dozens of people in various Federal agencies who have been working to undermine President Trump and could plausibly be identified as "THE whistleblower" in a legal proceeding.
3. There is ONE "whistleblower," but it is not Eric Ciaramella.
So putting some guy named Eric Ciaramella on the witness stand and questioning him as if he is the "whistleblower" is not only pointless, but it seriously damages the credibility of the defense.