The goal of his exercises isn't so worried about developing "six pack abs" and are more concerned about giving the abs a complete workout from different positions so that the body can be properly conditioned to perform martial arts.
It is true that many martial artists have the kind of abs that other men only dream of having, but that isn't their primary goal. It is really just a bonus side effect.
We should note however that if you are overweight that to get to that point however you first need to do lots of cardio so you can lose your extra belly fat.
Ab exercises are really more about toning the muscles. Ab exercises don't burn that many calories because people only do them for short periods of time.
Same goes with weightlifting - it doesn't burn a lot of calories because most people don't have the energy or stamina to weight lift constantly for an hour without a break. It is a myth that weightlifting burns a lot of calories because the stats on various websites giving caloric estimates that don't specify how many reps, how much weights, how much break time, how quickly/slowly is the person performing repetitions. There are too many unknown variables.
Both amateurs and professionals take breaks in-between exercises such as weightlifting. Ab exercises are, basically, a body weight exercise in the same way that chin ups and push ups are also body weight exercises. So don't expect to lose weight by doing ab exercises. Quite the opposite, you will probably gain muscle weight within the first couple of days of performing ab exercises.
If your goal is to lose weight and eventually get six pack abs then you first need to focus on some cardio activities such as running, jogging, swimming, cycling, or even just walking. As you progress you can also add activities like yoga, boxing, martial arts for fun. Then as you near your goal you can start doing more ab exercises.