The category actually does not exist
It would be better to clearly define Hask, and either fix it to be a category, or admit it is not a category with a clear explanation of what is broken and what can be saved. (Formalize fast-and-loose reasoning.)
Looks like some of the information in the table is wrong.
u2 _ = () is of type
Empty -> (), not
Empty -> a. As it stands, we don't have a real failure condition for the terminal object and arrow if you accept
undefined :: Empty.