“Oh, and you know what PR’s hate more than sitting in on interviews? Journalists commenting on the fact that a PR was sitting in on an interview in the copy. Let’s be clear, the public do not care about this, and it doesn’t make interesting copy. It’s petty point scoring that just sours your relationship for no real reason.”Two things on this. Firstly, as a member of the public I do like to hear about this. If there's a PR in the room, as the interviewee suggests, it means the subject can't and won't be as open as if they weren't which is presumably why the journalist mentions their presence.
(B) Interviews are boring. If you're a fan of someone, you'll read dozens of interviews with them and there's an element of churn, the same stories over and again. What makes them different is the journalists and although some would prefer them to be anonymous stenographers, some of the best interviews I've read have been about the journalist as much as the subject.
There's a balance and sometimes it can go wrong, but in the main, when a journalist mentions the PR, they're doing their job properly and probably producing interesting copy around that which isn't just reproducing the contents of a press release.