I mean, I know for STL, there are two things that are basically necessary for a 1L SA: Strong ties to STL and diversity. If you are lacking one or the other, stellar grades might make up for the difference. Probably not. After you meet these necessary requirements, then you need to beat out the other diverse people with strong STL ties in the interviews (the STL firms also look closely at your diversity statement/cover letter/whatever documents).
There's optimistic, and there's deluded. I don't think it's cocky for a SLS student to feel confident about landing a 1L SA, especially assuming good grades. If you have strong ties, there's nothing wrong with confidence either. But if you don't have ties, are a white man, and don't have stellar grades or attend HYS, it's just not happening. Not even if you give the best blowjobs in the world.
I also wasn't saying this person was cocky because of their confidence. They are independently cocky. Idk how arrogant people stay that way when the get their grades back but who knows. People still judging others by cold call performance in the Spring is just lol.