They moved the goal posts to misrepresent Grover speedup. Taking an oracular result and opening the box, in almost all cases, changes the query complexity speed up. Yes we've known that since, well since people thought about oracular speedups. Periodically someone notices this, writes up a paper pointing it out, and then promptly is forgotten about because it misses the point.

Further they completely ignore that when you open up the oracle like they have done, the problem they are considering is really CIRCUIT-SAT, and in this case the grover algorithm yields a 2^{n/2} algorithm whereas the best classical algorithm is 2^n. That the classical algorithm cannot do better that 2^n is the "exponential time hypothesis". I don't think the authors want to claim that they have disproven this hypothesis, since they didn't really. They just showed in some cases, in CIRCUIT-SAT, the problem is easy. This is a fairly benign, "yes...and....", statement.

So I think this is word games where the game the authors has played is to chose the worst words to describe their result. It's a bit sad because the authors are trying to think about the role of entanglement in these algorithms, and where entanglement is low we know that we can efficiently simulate classically these quantum systems.