At my undergrad, one must be a sophomore, and it is held in the fall. So yes, PNMs have had a year to hear rumors, be annoyed by sorority cheers, date/hook up with the "wrong" guy (ie an ABC's Boyfriend), or even gain "bad" reputations.
AND they also have a year to meet friends who are in sororities, get good grades, find their "niche," and explore the rumors themselves, only to change their minds about sororities and decide to rush in the fall. I didn't even think about them until the spring before, and researched over the summer...
I have seen some dirty rushing, evidenced by freshmen at the bars (grrr) but you keep that in mind for the fall and there are PLENTY of women who sign up on a whim the next year too.
I really think that deferred rush promotes what higher education is all about, learning and growing as an individual. The women have time to figure themselves out and adjust to college life. Though rush is held during classes in the fall, it is spread over 1.5 weeks, since it usually will start in the evenings. Also there are four sororities total at my alma mater, 3 NPC and 1 local. I guess that makes it a bit easier to get done during the school year.
When I found out that a lot of large schools do recruitment BEFORE school started, I was shocked! There was a lot I didn't know-some of your schools really don't mess around!