The author has a rather loose and imprecise definition of “cult”. As a result, many religions and other belief systems fit his description.
He should study the subject further before rendering the word so useless.
For the record, I never defined “cult” in any formal or precise way, on purpose. I also didn’t attribute faith in God or a particular religion as a cult. These are signs not definitions. Feel free to (please) supply me with some formal definitions and let’s see if the signs apply.