Not being a girl I could never Rush sororities, much as I believe I would have been an awesome sorority member

I would have loved

to live in the house and attend sleep overs, pillow fights, and pajama parties (that is what we guys assume you ladies do when you get together, so please don't spoil it)

Hmmm, sorry my mind was kind of wandering with that vision . . .
However, for all the people that may be a little taken aback by advice consider what people are really saying:
The interview analogy is very valid. The first rule is don't dress in a way that takes away from yourself. Clean and neat are the basic rules of thumb.
Remember that you don't know these people, so they won't know how cool you are really. So the trick is not act or dress in a way that fits a negative stereotype.
Its not that people are being shallow per se, but people tend to pick something and identify you with it. Especially if they don't know you. And most of the girls won't meet you at all.
So PNM 1 becomes the girl with the red hair that smiled all the time . . . to the girls that just remember seeing her.
Lets say PNM 2 talks with a sorority girl and really hits it off with her . . . but it might not do much good for the girls that didn't meet her to be referring her to as, oh the girl with the dirty fingernails! Or the girl who's breasts were falling out. They aren't being mean really (most people are only truly mean to people they know) its just an identifying characteristic.
Plus when someone is being disqualified for something, its not necessarily dirty fingernails . . . but if you can only take one out of three girls in front of you, and each girl has someone who met them and liked them, but one is remembered for some negative thing that stood out, I am sure its going to decrease her overall chances in a vote: by comparison to the others who seemed equally nice and cool, but the Chapter can only take one girl . . .
As far as people over whelming with specifics. They are just responding to people's desire for very direct directions. For some people you can say, formal, or clean and neat and everything will take care of itself. Some people are mosre comfy with the idea of knowing the best color, or fashion combination. For guys even, formal could mean sports jacket and slacks, suit and tie, or tuxedo.