> How can either side get an accurate assessment of the other in such a short time?

There is little evidence that longer interview cycles produce better results.

"Years ago, we did a study to determine whether anyone at Google is particularly good at hiring. We looked at tens of thousands of interviews, and everyone who had done the interviews and what they scored the candidate, and how that person ultimately performed in their job. We found zero relationship."

- https://www.nytimes.com/2013/06/20/business/in-head-hunting-...