You can read into the RFI what you will, but the clarification issued on 7/10 says that the sustained g is "for purposes of APT requirements".
I believe that the USAF wants the student to experience, in a real aircraft, rapid onset (in the RFI) followed by sustained g through 140 deg. of a 180 deg. turn. The 10 per cent limit on speed loss, I would guess, is to ensure that the aircraft is more or less in a steady state (like a fighter) rather than bleeding speed like a stuck pig. Entry and exit altitudes may be safety considerations.
So IMHO the idea is to deliver the fighter g experience without the thrust and expense required to do it in level flight at 20kft.