A lot of doubt being expressed here. Tanis[0] was identified as potentially preserving the moment of the KT impact by 2013, and I believe this identification is now established beyond a doubt. The paper [1] makes the case for it. I've read it (review at the time at [2]), and it's solid, with multiple lines of evidence connecting it to the KT event. Most convincing to me is the tektites found in fish gills: these glass beads are considered a sure marker for the KT boundary, and the fact that they were taken in by fish in large numbers indicates they must have been floating in the water at the time of formation. If you don't trust me, on the authors list are Walter Alvarez, half of the pair that originated the impact hypothesis in the first place, and Jan Smit, another world-leading expert on it.

[0] https://en.wikipedia.org/wiki/Tanis_(fossil_site)

[1] https://www.pnas.org/doi/10.1073/pnas.1817407116

[2] https://news.ycombinator.com/item?id=19548093