In my instruction manual for FFX-2 it credits the voice actor that plays seymour but i've completed it an I can't recall him in it at all. Why would they credit him in the manual?

I think you come across a sphere with him in it or something iirc. It's either that or something else since I have him in Shinra's Dossiers.

Ah right, I never really watched all the spheres I collected so that makes sense.

Yeah he's in Baralai's Sphere. That's it, though.