Sorry. What I meant to say is that it's more than likely because of Koda Kumi. Square probably did not see a point in paying her extra money to use the Japanese versions of the theme songs outside of Asia, because at the time, there was no intention to release an unlocalized version worldwide. She initially recorded her own English versions of the songs, but her accent was way too thick and was therefore replaced with Square's own localized version performed by Jade Villalon (credited as JADE from SWEETBOX). Either Kumi's music isn't licensed here (more than likely, because iTunes won't even let you purchase them, despite listing them), or they signed an exclusivity deal with Villalon. They probably thought that it wouldn't be fair for one game to be dual, and one not.
Again, this is speculation.