DD, I think it has to do with hand placement. In SOB with mag down you need to slip your hand in between the gun and your body to get a good grip on the pistol. Mag up your hand can grip the gun easier for a more secure draw. Also mag down draw, the gun when pulled out needs to be turned, either pointing back at your body or swinging around sweeping somewhere else. Just my thoughts with NO good or bad leanings.
Be safe.

Pinnacle: I also love my Blade Tech SR for my PCR. THERE thread is NOW back on track!!