Beating gcc/clang/icc is not a trivial task. One can engineer the pair `{benchmark compiler pass}` in such a manner that they show a speedup, but over a benchmark suite say like the SPEC suite, general community consensus is that it is very difficult and their paper doesn't reveal that they've found a secret sauce (sauce := compiler pass).
My claim is that there is no additional information that Python provides as opposed to C that would make it faster. And hence, the only conclusion I have is either they have supercharged their compiler for that particular benchmark OR they have chosen to handicap C as once can express the computation in C that emits the same assembly that they lowered to and hence my point on handicapping the C benchmark.
One must note that this is impossible, unless you have chosen to handicap the C-implementations while benchmarking. Borderline unethical IMO to put forth such a claim.
For postdocs, the situation is even worse. Postdocs typically get paid ~1.5x that of a PhD student. And in some fields that are closer to the Basic Sciences, one (virtually) cannot land a permanent research position without spending 2+ years as a PostDoc research associate. The current generation of professors are the worst folks when it comes to the reasoning about sustainability of research in their field.