If Harry brings his very own journalist, the one thing they won’t be is neutral.
IMO- this just serves to further exacerbate everything.
I honestly don't think things can get much worse between the two sides at this point; that William's friend is openly speaking to Robert Lacey seems to be indicative of that. Having a self-selected journalist there may evoke a few eye rolls behind the scenes at KP but I can't see it making a huge difference.
I suppose neutrality is in the eyes of the beholder. Harry clearly doesn't feel he'll get a fair shake from the Royal Rota; I think there's some truth in that but I don't want to get too off-topic.