Yeah, my thought is there's a clear chain of command. Even those controlling others are controlled themselves. Both Reyna and Po are being controlled. Po apparently got too close to someone in the past and was then told he had to kill that person (I'm trying to remember that dialog, though, so there might be more to that). Clearly his boss values anonymity. He probably figured even a whisper would be too much of a risk.
The line about the clairvoyant being someone with a lot of resources instead of psychic powers struck me as being the key why it wasn't Po. Since he was in prison, he wouldn't have had anywhere near those kinds of resources. I also think that's the truth since they seemed to try to quickly bury it with a fake out right after (something about Fitz saying that, if he were clairvoyant, he'd try to win the lottery).