Equivalent of "Are you sure?" pop-up when you try to delete a bunch of files, or close several browser tabs.
If the UK's still sure, it will deliver the same result.
After all, the best way to silence irritating critics is to *prove* we still want to leave the EU!
And if the mood has changed, then, well, the "we won get over it" narrative is dead.
Either the result will be the same, in which case the noisy remainers will shut up (or at least go much more quiet than now!)
Or it will be different, demonstrating how essential it was to double check the original decision.
If, on the other hand, support for Leave collapses, that shows people changed their minds between an "abstract" Brexit concept, and the reality of actual Brexit.