Confused.
Why the 3 day timeframe?
Why Hanscom? AFMPC does not take into account where you went to college, it is if there is an opening at Hanscom for a 2nd Lt. and your DS's AFSC matches up.
Also, the way it typically works is they will go to some type school for career training before they show up to their 1st base. That is a big reason for the delay since they can only get so many through those schools at a time.
AFA grads go before ROTC grads. They also try to send those that commission earlier before others. I.E. VT will commission @ 3 weeks prior to your DS. Thus, if his career field is in high demand, such as Intel, or UPT than their report day will be that much of a longer wait. Think of it like a queue.
Report dates are not firm until about 30 days prior. They can change. Our DS's changed 4 times.