Generics allow writing of algorithms—if you're writing a 'sort this array' function, why do you care whether the elements are integers or strings so long as you can order them.

I do, however, agree with you in general—it seems like he's trying to re-implement generic serialization. Otherwise, it's difficult to see what a 'Bit' (for instance) has in common with an Int and not, for instance, a double.