There are safety in numbers: for many 4.0 students there are ones who barely scrape by with a 1.67. I say that in response to OP’s original question.
The most telling sign for me is the ‘new member’ GPAs. In some cases they buoy the overall organisation’s GPA, but in a lot of cases they do not. Unless students have a very good GPA foundation their first few semesters, as they move into harder, upper-division classes, often the GPA will dip. It would be great to have this info by major/college!