Well I just got reunited with Isaac and found out that yes, it really does matter if you transfer data over or not, because there are 2 Djinni you cannot get, and a forged weapon (cursed, but I just have a THING for having everything), at the very least, that you are <censored> out of if you don't transfer data, because you need the Orb of Force for the Force ability, and also the Lift ability (which if I am not mistaken can be used elsewhere but I haven't checked yet) to get both Djinni, and you have to have transferred data to receive the Orihalcon at Atteka Inlet.
So.........having saved after reuniting, now I have to restart after some 36+ hours game-time not counting resets, mess with the coins in the fountain and the stupid game tickets again, and do that 'lovely' battle with Poseidon again, because I * refuse * to miss out on any part of a game experience. Needless to say I am ready to single-handedly throttle every single member of the GS2 programming staff barehanded if I ever got the opportunity right now.
What kind of <censored>s think up this stuff?