I think that boils down to how much they could fit on 2 disks. Had to cut corners somewhere. You also gotta remember for the 360, a lot of content had to be present on both disks, kinda limiting what else was there. (All armor, weapons, attachment code, engine code, most SFX, etc)
Then it’s as my friend said (though talking about Tales of Vesperia at the time), maybe they should have done an FFXIII and put it on 3 disks.
On a side note, the time frame for swapping disks is fucking retarded, instead of it playing out like ‘finish the second assignment from Mr. bright and cheery and then swap disks’ instead you don’t swap disks until actually going into a disk 2 mission, stupid because all the disk 1 areas are accessible in disk 2 >_>