The idea isn't necessarily what works for you in self-defense, it is making sure that you fully understand the material. I'm not going to promote someone in a style that incorporates both grappling and striking for instance, if they only know how to escape while grappling so they can win with standup. They're winning they're matches but not going up in rank.I would have thought you would want to apply what works for you regardless if it is self defence or otherwise.
But otherwise if you think there should be a syllabus. Then you can still test that rigourously.
Also, just fighting won't get every aspect of self-defense. They could be winning, but do they know how to knife-fight (part of what my bb required)? Do they know weapon defense, how to deal with multiple attackers, how verbal deescalation works? Without these things, they're not getting promoted past a certain point.