One issue is that to take advantage of a secret is that there are lots of ways for the secret to not matter.While hiding your true skill in a main focus area (like music skill for us) isn't too useful, there is still some merit in secrecy, specifically because it can let you eke out a win where otherwise you would lose. Take the case of CtE; someone who doesn't know to put distance from us if they're tagged by HR is liable to get hit by the full effect, very likely ending a fight right there.
In this system a win like this has knock-on effects, either a few AP worth of CP from a successful defense (and appearing weaker than you really are makes you more attractive of a target) or a jump to a new rank you might not have made if your capabilities were better known.
Like, lets take the situation you outlined. We have CtE, which we kept a secret; therefore, our opponent doesn't know to keep their distance; therefore, we get CtE's main effect off on them in the duel. Winning the duel gets us several AP worth of contribution points; does that mean the secret was worth several AP? Consider:
- Even if we didn't keep CtE a secret, our opponent might not have known about it. We don't see the techniques of the people Ling Qi is challenging, so it is not at all clear that someone challenging us would know all of our publicly-revealed techs.
- Since our opponent chose not to keep a distance, if we assume that decision was logical (before you count CtE, anyways), you might presume that they prefer to fight at closer range. Given that, even if they had known about CtE, they might have acted the same way, or if they did avoid close range that might have cost them in terms of what they could do in the fight.
- When we use CtE, it is not certain that it will hit and end the fight.
- Finally, it is not clear that we couldn't have won without pulling out CtE as a surprise.