Ok, so you have already approached your Prof. and you were given the explanation
a carbocation with resonance is always more stable than a carbocation without resonance
So make sure you understand whether this statement about carbocations is correct regardless of whether or not it applies to the question asked.
Ask about the relative rates of allene formation and where you can find this information (as Orgopete
says, preferably the primary literature source)
Don't go in all guns blazing thinking that the academic has got it wrong, if they have made an oversight they may not appreciate being confronted on their competence at question writing.
Instead approach the Prof. with the attitude of general interest in allenes and the kinetics of their formation. If they have made a mistake they may thank you for highlighting it (they are only human after all).