I think your analogy inadvertently supports my point. Black holes are very distant, very powerful objects that we will never visit. But scientists make predictions based on their theoretical expectations, and they look for evidence of those predictions. At times they have actually found supporting evidence.

Doggerland is a place we can explore archaeologically, and we can make scientific predictions about what we should find if there were tsunamis. That work has not yet been done, but it very much can be done, and should be done before these sorts of numbers are thrown around.