I do agree with the statement in the article in cooldowns being an under-studied topic. Much has been conducted in terms of warm-ups but not so much on the cooldowns.
Related very much to the point above in the KK post is what I heard years ago that the importance of a CD after any workout or meet was in bringing the various systems involved down to the baseline in unison. That is particulaly in runs of approximately 300m+ where lactic acid was prevalent was that the heart rate would drop at a faster rate than the blood vessels would re-constrict leading to low blood pressure. If one could continue jogging or at least walking fairly briskly for a few minutes (how many I don’t recall hearing, specifically) after the race or exercise bout, the heart rate could remain a bit higher while the reconstriction could occur thus keeping the blood pressure drop to a minimum. Again, I have no evidence of this nor any physiology book I could point to as the source for this information but it is something I heard years ago.
Another point of the CD as I heard it was that by keeping the HR up for a while longer you would have a better opportunity to flush out metabolites that won’t be as easy to accomplish with a sudden stopping of all activity.