The question is not can? but did?
I don't know how NIST arrived at their number, but there were videos of its final approach, so it should have been a simple question of, how much time was this airplane taking to get out of its own way? Given we know the airplane's exact length, it shouldn't be much of a challenge for the likes of NIST to derive a reliable estimate of its velocity, Pratt and Whitney and pilots' folklore notwithstanding.