I'm guessing that that have a Document Forger club, one with close connection to the local al-Qa'ida recruiter's office. I'd be surprised if these guys are really 'students' at all. A student visa might be a great way to get into the U.S., but I'm guessing that these guys already have a complete education from the Martyrdom Institute of Technology.
They could have fake names, forged passports, and no history. Worse, they could have friends already here, ready to hide them in safehouses until they're needed.
Remember that the Muslim Brotherhood is big in Egypt and has ties to AQ - could be the MB is planning something big to impress AQ.
Lat's take a guess that the three denied was deliberate on the Muslim end....but it's a sham. The three they really wanted in came earlier than the 17 who did get in. Kinda like the pea & shell game.