Hi, Ellen. The benefit of that category is that I share it, and just checked and you and I are 8th cousins once removed. Which doesn't mean I'll get invited to Thanksgiving dinner, but it's a fun connection, nevertheless.
I thinking where such categories are useful and where not, it would seem like (1) showing descent from very very distant ancestors is not useful. Like Charlemagne, whose genes surely flow through 95% of the living members of Wikitree. Similarly, (2) placing the category on intermediate ancestors is not terribly useful. My great-grandmother is the ancestor of a hundred descendants and the descendant of thousands more -- why categorize all the people she's descended from or ancestor of?
Where it does seem to have some value is as a category placed on the profiles of LIVING members of WikiTree. Because if I'm in the descendant category, I can go to the category page and see what other living members of WikiTree are also descendants. Now THAT's interesting and potentially useful, although it probably won't get me any turkey.
Now, while I'm a descendant of millions of ancestors, there may be just a few that are particularly interesting, possibly Revolutionary War soldiers or Gateway ancestors, so I'd create a category for that person's descendants. I think that was probably the motivation behind creation of Harrington-100's Descendants.