The courses do not guarantee depth...
Water rescue techniques are taught in the courses.
CPR is not only ineffective but can also be dangerous to a blackout diver. When a diver blacks out the epiglottis closes to prevent water from entering the lungs. Without reviving the diver, trying to force air into their lungs can won't do anything and you can potentially damage tissue. Also the main premiss of CPR is circulation of blood. The idea is that there is enough oxygen in the blood to prevent tissue damage. periodically adding enough air to the lungs to replace some of that oxygen. When a diver has blacked out the blood is oxygen depleted and the brain is doing everything it can to conserve oxygen and keep as much of it in the brain as possible. CPR would fight both of those natural mechanisms.
There is a bad misconception among those who haven't taken the courses and many looking to take the courses that they are all about depth. While you may increase your depth by taking the course this is mostly a product of proper technique. The courses focus primarily of safety, technique and physiology.
That being said the courses can vary widely from instructor to instructor. Some instructors prefer a more "hippy" style that includes a lot of meditation and other forms of relaxation. Others take a much more scientific approach. In my opinion these are the better and more practical courses.
Clearly there are different levels of quality, but there are a basic level of information and technique that, when applied properly, can improve diving. You can learn many of these with years of practice and from more experienced divers but the courses can condense and shorten this learning curve. You can teach yourself to read but it is still much easier and faster to be taught by a teacher.
If the diver in the video had taken a freediving course he would have known how to revive his friend and many of the factors that resulted in this event could have been prevented.
Sorry, I didn't intend for this for this to become the rant it did.