Singer denies the validity of mathematics concerning video poker. It's just not true. Singer offers anecdote after anecdote. Like the time he played Double Double Bonus and made a bundle. Every player has stories about the times he won and the times he lost.
Every player has some of each.
For expert players, our year-end results are usually positive. For players subscribing to Rob Singer's philosophy, their year-end results are usually negative. Using the mathematical methods leads to good results. Singer calls all of the authors listed above as Bob Dancer clones. Dan Paymar, for one, has been a video poker writer for years longer than I have.