Hm, I'm not going to comment on specific cases, but it is highly unlikely that BB is a game of pure Math. A random element must exist.
Upsets happen. You may have statistically played them off of the park, but I would assume that on odd occasions you will still lose. In these cases it will cause confusion (or as you put it "paints a very poor picture of what happened").
The picture painted may be poor, but more often than not if you win in the match ratings you will win the game. Please note, "more often than not", rather than "always" is a phrase I have chosen for a reason.