Hi Nim
Durn! I can't get your film to run...I keep getting dumped back to my desktop.
I searched the past posts and found that I have to have the same version as you...and maybe the same terrain? I'm running the latest download with no modifications.
None of my earlier films run either.
As for your question, the defensive barrel roll is not the same as a rolling scissors, although it's possible that the roll could set up the chance for a scissors.
The defensive barrel roll is a maneuver designed as a guns defense. It makes the attacker have a tough job trying to track you. If flown aggressively (and with a power reduction), it may force an overshoot ( a 3/9 overshoot, not a flight path overshoot).
A lag displacement roll in an offensive maneuver designed to improve an attacker's offensive position...by either reducing aspect angle or increasing range. The defensive barrel roll simply keeps you alive a little longer. It does not guarantee that an attacker will overshoot, it only makes his gun attack more difficult. Also, it does not necessarily increase angle off or range unless the attacker makes a serious BFM error in response to your roll.
Andy