Apparently the reason why they do those crazy hand gestures is to sustain the sound of the string... So like the hands don't mess up with the soundwaves. Also the delay in immediately placing your fingers on the strings after plucking prevents that buzzing sound when you touch a vibrating string.
Also I've heard it helps the player keep in rhythm...
Salzedo style is a little too fluffy for me though. Not sure if Grandjany is any better though but at least there's less raising in that style.
PS: can't wait to actually get a harp teacher... At this point in time my current technique would give any harpist a serious heart attack.