In Spare, Harry says it was KP and while Spare was definitely an interesting read, the things he got wrong are varied and many. The book had no fact checker. He's an unreliable narrator, as I think most of us would be after losing mum so young, having the world so interested in you, being teased about your parents affairs.
The Cut accused KP, but that was never proven. Daily Mail complains all the time that William and Kate don't talk, unlike Diana, Charles, Harry...they play it like the Queen.
Honestly, I have no doubt the stories came from other royals. Camilla leaked meeting William and Charles leaked Harry's drug problem.
But other than Jason Knauf coming out and saying he personally had to intercede in bullying of staff, no one from KP has been proven as planting stories, that I've seen. And Jason stood by that (which I think is more a American/British culture/work issue than Meghan being a bully). And of course, the Sussex have had to apologize a few times for misremebering under oath.
I will say, I do think William capitalizes when a "Harry and Meghan fly in private plane" by flying commercial or taking the train after. That's laughably lame. I don't think he leaks anything; he's always been very clear that he understands that once you let them in, you never get them out.
