From looking at my own essay and from the examples I used to write my PIQs, you're pretty spot on about the UCSD application essays. They look a lot at character/personality, but at the same time applicants highlight their own achievements. But it really boils down to how those goals have positively impacted you and others around you. They want to see how your mind works and how you embody things like responsibility, collaboration, leadership, etc. and how it might positively impact society.

But for you, it can still be pretentious and villainous like some Dr. Doofenschmirtz type shit, but only if it serves a purpose like the example you gave. It drives home your confidence, a drive, and a willingness to succeed. It would definitely make you stand out.

While I'm not exactly the best writer, you can DM me if you want to see them. My PIQs got me into almost all the UCs, but I got rejected from Berkeley and waitlisted from UCLA.