Actually it is provable. Look at the star positions, look at the geological evidence, the biological evidence and so on. Unless you are a creationist then this is a good case to explain otherwise inexplicable events in the past.
By the way, the article credits Graham Hancock as the originator of the idea base on his interviews with the original chief archeologist about the meanings of the cravings.
If you have not read Hancock’s book - “Magicians of the Gods” - then the theory goes on to state that the comet was one of two, the other previous one initiated the Ice Age about 6,000 years prior.
Both comets were on the order of one mile in diameter and part of a larger body which had been broken up millions or billions of years previously. This body forms a torus through which the Earth passes each year producing the Taurids meteor showers.
The theory further goes on to say that the stone is not just a record of what happened then, but a warning of what WILL happen again at some point between now and 2060. In other words, large body strikes on the Earth are, geologically speaking a common event, we just happen to live between events.
That the site was intentionally buried has been a mystery; however, if the builders wanted to preserve their record and warning, then burring it to protect it makes sense.
Who were the builders? Survivors of a previous and largely unknown but advanced civilization - possibly the builders of all megalithic structures - none of which we could make today.
Theory...theory...theory. Hmmmm. Far out!
Hancock does a great job in his book. He explains well, what we already know. And, there may have been more than one, but the main event was clearly about 12,800 years ago, as the study of the ice sheet dating shows.
Here is a NASA photo of the “comet pieces” on Mars. It is most probably debris from a supernova explosion that passed through our solar system. Some of this debris would have been captured by our sun’s gravity to become a long period comet, or, perhaps we were hit, along with other planets of our solar system by the initial debris wave. But yes, we do cross that comet’s path.
https://www.nasa.gov/mission_pages/msl/multimedia/pia16204.html
Worlds in Collision, 1950, by Immanuel Velikovsky poses a similar theory and lays out the evidence available at the time of writing. It has not been disproven, yet.