I just followed @Lee-White 's suggestion of watching the flip through without sound. Even though I had been a bit sceptical with the sound on it surprised me how few pages he compared and how dissimilar the page layouts were.
Even more obvious was how many pages of Parker's are skipped, and how much scrolling back and forward Dunn has to do through his own book to share the examples - the charge that the order of presentation is too familiar relies on the order he was showing in the video.
It is amazing how damning things look when presented with emotion and story.
Whether Parker has unintentionally absorbed too much of Dunn's terminology to have crossed a line in his headings. I don't know. But the claims that are being made against it that it is almost identical I don't think will stand up.
What a mess. It does seem a good example of confirmation bias. Suspicious of Parker's book from the few previewed pages, a shocked watch of a flip through had him pick out similarities whilst dismissing differences as attempts to disguise similarities.
I feel for him, it must have felt awful. But he could have raised concerns with his publisher and they could have got lawyers to look at both books and delay/stop publication if necessary.
But what he has done instead leaves him open to legal action for defamation and loss of earnings.