Answer to title: No.
Think of all the qualities it doesn't measure.
Plus MCAT has at least 2 serious flaws:
1. The test maker sometimes overlooks, or fails to think of, other completely valid perspectives.
(Example: A stand-alone question that says, "What can cause X? Answers choices: A. Y can. B. Z can. C. Q can. D. Y, Z, and C can." The answer might be Y can under certain circumstances, and Z can under other equally common circumstances, but Q does the opposite and clearly cannot cause X. There you have it, 2 valid answers, where there is no "best" answer because the test maker completely overlooked something about Y or Z. Test makers are imperfect human beings too. Minimizing these imperfections likely requires time and money so there's only so much that will be done to prevent it.)
2. The easier problem to prevent is one of setting a bad example: Unlike most other professions, the answer keys of most MCAT prep material is littered with insults, put-downs, belittling, and discouraging harsh remarks (and other negativity) aimed at students who choose a wrong answer. Ask anyone in a non-medical profession, and most other (not all) will agree that this is inappropriate, contagious, and ultimately harmful. A better choice would be a neutral* (non-insulting, non-belittling answer key), or better yet, an encouraging* one.
(I believe that pre-meds look up to advisers, adcoms, professors, and doctors, in a similar way to how a child looks up to a parent and older siblings, and in a similar way to how anyone might look up to a role model, and that what's said in MCAT answer keys works it's way into the next generation of doctors. Patients will ultimately be on the receiving end of whatever culture is set at these early stages.)
AAMC is better than most of the test prep companies when it comes to this, yet still has plenty of examples (of #1 and #2 above).
*TBR deserves credit for the encouraging statement on their books, "If you study, it will come." I find that tone far more appropriate and helpful, than negativity.