That is true, interviewing bestselling novelists can be as useful a qualification as actually being one when it comes to working on a book on writing bestsellers. And the fact that your book was picked up by a fairly well known commercial publisher and attracted favorable reviews of its own shows that you know how to write.
In this case, however, we have a book that was written about writing bestsellers that was self-published, instead of attracting the attention of a commercial publisher. And someone who is touting a system that enables anyone to write novels, devised by someone who apparently is not using this system at all - or is, but can't use the system to write a publishable novel. I'm not sure which is worse.
That does not in and of itself say this book is bad, but it really makes me wonder.