They are right in their own sense. Reason is that this exam is much different as compared to other usual exams. But their also many examples of people who prepared for the exam at the eleventh hour and were allocated.
Where does lie the difference? It is in approach,previous knowledge and above-all one's burning midnight's oil. Do your and leave it to Allah. You can do but be sincere and totally focussed.

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"But screw your courage to the sticking place,
And we'll not fail." _Shakespeare, 'Macbeth')