I am guessing that Parrella is privy to more info on Nebraska kids than any other coach in the country. If they're waiting for some reason to offer that's fine. It could be they want to see some academic progress or they may know something the other schools don't. It would be uncomfortable to offer a Nebraska kid, have the kid commit, then have to pull the offer because of a lack of academic progress or other issues. It's a pretty common practice to not offer kids until they have a chance to work with them in summer camps.