People keep saying in this thread "there is nothing stopping people from using the same method" to do something else! I think that this is an irrelevant criticism. This is a valid attempt to minimize the amount of information collected on visitors and still providing a unique visitors per day count, and the fact that someone could build a similar but different system that looks like a cookie isn't relevant.
They demonstrated a PoC that uses an HTTP feature in a way it wasn't intended to add entropy to fingerprinting techniques. Discussing how this same exploit could be used maliciously by others and how to prevent that isn't criticism of the PoC, it is standard security practice.
