GS and Super-G poles carry a deep bend that wraps the hands in close to the body, so a racer can hold a tuck without the tips swinging wide. That bend is the whole point: a straight pole in a GS tuck puts the tips out in the wind and the hands in the wrong place.
The larger the turn, the more bend and the more length you want. Super-G and downhill poles are longer and more curved than GS poles, and many athletes run a different pair for each.
Length is set by the athlete's height and the discipline. Get it wrong and the tuck is compromised, so measure rather than guess.