The "flood" occurred during historical times, ca. 4,350 years ago according to biblical scholars, so you need to be looking not to geology but to archaeology and sedimentology for evidence. Sediments of that age have been quite well studied in most parts of the globe, and no evidence of a worldwide flood has been found.
But back to the article...why would the earth’s rotation slowing cause a release of heat? I don’t get that claim.
If the rotational energy was changed by slowing, there would be a release of heat. But the article is wrong in equating a leap second with the earth's rotation slowing by a second. They are two different, and unrelated, things. A leap second is equivalent to a leap year, in which an extra day is added. That extra day does not mean the speed of the earth's rotation has changed in any way; it serves just to adjust our calendar to the true length of the year.
Well, there’s quite a few “biblical scholars” out there who do not think with the mind of the Church, and I am of the school that in the face of apparent contradiction we should take an attitude of “hmm, well that’s interesting” and wait a few hundred years to see what shakes out.
A date of ca. 4000 B.C. would certainly suggest (barely) historic times, and current dating in archaeology would lead one to believe Homo sapiens was already dispersed by then. But perhaps there is something fundamental we are missing in this equation—either from a scientific standpoint or an exegetical one.