Fantastic that you asked the question, not brilliant the mathematician gave you the wrong answer, He obviously was no physicist :)
He might have done so with the best of heart I guess, but it always sounds better for our prospects of attracting investment, or getting a job, or selling a book we wrote, or even just selling our dialog to a bunch of schoolkids, if we quote our long list of qualifications, and talk as if we know everything about everything, then our audience is more likely to buy our story. This is part of the profit driven issue we are seeing lately with nobody knowing who to trust in government, or any authority, even science, definitely never trust historians imho, which brings us to this asteroid.
There is the possibility that it wasn't an asteroid that did the damage.
Further, even if it was an asteroid, it wouldn't have needed to be a direct hit, for an asteroid to do that amount of damage, it could have been by a near miss, in fact if there was no change in earth's mean trajectory, more than just a wobble, then there was no collision with anything of significant stored kinetic energy. This is actually proof that there was no major asteroid impact.
Amazing how a history of billions of people driven by profit actually wipes out all history, look at the statues being torn down, the artistic artifacts being devalued and destroyed, the pyramids would have been gone long ago, dismantled by humans for profit, if they weren't so indestructible.