Is a 6-point difference substantial in a statistical sense? To me it seems small enough to be noise.
According to the paper, the validation set has 107 problems so it's a difference of 6 problems solved, not just 1-2.
Also, it's not a typical eval with multiple-choice answers — these are difficult coding problems from competitions where the answers are strings or integers, so the odds of "guessing" a correct answer are very low.
To me it sounds huge, but if there are only 16 questions, then yeah, it’s not significant.