All this means, in the context of WikiTree, is that some person who is a descendant of that medieval person has added their DNA to their own profile. Overnight WikiTree propagates the DNA to all ancestors of that person. Additionally, YDNA and MtDNA are propagated down other descendant lines to the end of their lines in more recent times.
Eventually, with more YDNA, for example, other descendants from that medieval person will post their DNA to their profile and it too will be propagated. This will either confirm the links or highlight a problem in the links.