Congrats on the score
You can have your test re-scored, but I doubt the score will change and I doubt, even more, they will clue you in on why it wasn't a V51, because doing so would tip their hat into their scoring algorithm, which I am sure they want kept a secret.
Just for fun: a CR problem involving real information to help you clue in on why.
UCF is the only undefeated football program in college football, however they are ranked #14. Clearly the ranking system is incorrect, since UCF should be ranked #1.
Which of the following, if true, would weaken the conclusion?
(a) Although UCF is undefeated, they played the worst teams in the league and barely won those games.
(b) UCF has never had to travel more than 250 miles for an away game.
(c) UCF's stadium is one of the loudest and makes it hard for opponents offensives to call plays.
(d) UCF is the only team in college football without significant injuries
(e) UCF has more seniors on its roaster than any other team
Of course the correct answer is (a). Played the worst teams (you weren't given enough hard questions) and barely won those games (GMAT doesn't give style points: doesn't matter if you can solve an question using 1 method or 3 different methods or blindly guess the correct answer
....it's a right or wrong thing, so we can eliminate right/wrong answers from your possible reasons).
If you think about it, the only logically explanation is that
you weren't given enough difficult questions. Now, why weren't you given enough difficult questions? I have two theories:
(1) You were dealt a bad hand of cards.
To use an extreme example, if I sat for the GMAT and was given basic arthritic questions (1+1=?), I am sure I'd get all the questions correct, as would most people; however, we both can agree that should not warrant a Q51. Ideally, yes, if you were answering all the questions correctly, you should have an opportunity for a V51; however, the GMAT may not be so ideal. Most standardized tests focus around the median score, and the accuracy of the middle percentiles, the extremes may not be perfectly skewed.
(2) Although the experiment questions are not "graded", they may affect the overall difficulty level of all the questions you see, and the overall difficulty level of the questions affects your score.
Essentially what I am saying is you missed a few of the experiment questions, which lowered the overall difficulty level of all questions presented to you, so even though were answering the non-experimentally questions correctly, they weren't the *most* difficult.
To test this theory, we can use reverse logic. I believe the difficulty level of your experiment questions are determined by your performance. I didn't score as well as you have; however, I can attest to the fact that I did not see any very easy questions. By very easy questions, I mean the first dozen or so questions that appears in the official guides.
This makes sense in that giving a sub-600 level experimental question to a 700+ scorer is essentially wasting an experiment question and vice versa... giving 700 level experimental questions to a clown
is wasting an experiment question.
Nonetheless, a great score, I don't think any school will consider a 790 any differently from an 800.