This is interesting, because I wouldn't be too sure about that. Whether I am able to play chess well exclusively depends on the strengths of my opponents, because there is no absolute baseline. If society somehow decided that what you were writing wasn't "music" anymore, you would be the only person left stating you had that skill.

I believe that most claims about one's own skills do come from outward judgement and interpretation of one's actions, not introspection. The only thing humans have is, to radically appropriate the jargon, a way longer context window (spanning over an entire lifetime!), together with many ways to compress it.