I watched this and another video covering the topic. I guess I'm just a little confused because the Inktober art book isn't out yet? They undeniably look similar, but isn't that because they're both tutorial books for the same kind of art techniques?
I wish they didn't postpone the book release. I would have liked to see it for myself to validate whether or not it was plagiarism. I don't take art theft lightly and I don't want to support anyone who does it, but I don't really have any way of knowing for sure until the book is out.