How-To-Write books?

Those who can, do. Those who can't, teach. Is how the saying goes. But is it really accurate? Maybe in some cases. In writing, I don't believe it is. It seems like every self-published writer also tends to put out a book touting their success and instructing other authors how to reach that brass ring of success. Whether they're actually as successful as they claim is entirely up for debate, as just about anyone can slap a gold star on their book and there's a hundred ways of gaming the system...