Years ago - different alias, different name, whatever----
I asked this same question. I felt what I was "seeing" was impossible. Basically, the explanation was pretty straightforward, I even think Pyro answered it (fuzzy memory here).
Basically, the answer was: What I was seeing was not representative of the true position of the aircraft in space. Lag, graphics capability, etc, etc... all caused the angle of attack/positioning of the target aircraft to appear slightly off of where it truly was. Another way to put it---when a spit was pulling back through it's lift vector after the merge, it might appear to be pointed straight up when in fact, from the target aircraft's cockpit, it (and it's pilot) are actually continuing a smooth transition back 180 into my aircraft. Visually, the angels were just a bit off. This usually only happens in quick/violent maneuvers. IN fact, just a few minutes ago - I jumped a 47 with a ton of E in my 190. It looked like the 47 slid on its tail while still travelling straight ahead. I know this was actually just a violent skid maneuver (nicely done by the way) that just looked like a UFO trick.
Hope this helps a bit.
Broc