Wisdom is for the purpose for auto attacks (when in battle go under tactics, anything BESIDES 'fallow directions or whatever it says, is an auto attack), the more wisdom they have the stronger attacks they will do on their own, or if you have them on heal they will use something like omiheal instead of useing heal on just one person.
I know for a fact that Wisdom affects a character's damage with offensive spells. I have never heard about that AI thing; what guide did you read it from? It is not rare for guides to contain false information.
You need to say more than you know from experience. Have you done any testing that controls for everything other than wisdom? Perhaps they use their more powerful abilities because they have more mp to use them with. mp would increase at level up just like wisdom. The notion that they would make the optional AI(which seems to be in place merely for time-saving) suffer from low wisdom does not make much sense.