Ah ok. I still think it is better off implementing minimax since that is such a widespread algorithm with many applications.
I still consider that list of rules an "expert system", since it is so coupled to tic tac toe, and isn't applicable to a wider set of problems. It's just that a lower level version of "expert" is required ;)
I'm sure it can be adapted to Connect4 though, but it's likely to run into a load of special cases and then you're better off using some kind of tree search like minimax instead.