Other built-in Tahoe apps have more consistent indentations and far more icons. The Safari team (not the WebKit team, the people building the app wrapping it) just phoned it in with the menu icons. They also somehow disabled the Tahoe window opening animation.
Yes, just consistently line them up and it would be fine. There’s plenty of UX research saying icon+label improves recognition and task speed. NN Group is a good resource for this.
I think it used to just mean "singular", from the Latin grex, gregis meaning herd, and e/ex meaning "out of". It could mean singularly bad or singularly good I guess in English, but in Latin I think it had more of a connotation of exceptional, extraordinary, eminent.