While I'm sure it was certainly an effort to retranslate SoulBlazer, I'm guessing it is just the script that was changed.
The bosses were buffed up in the western versions.
While often that has caused things like 7th Saga and Working Designs, I would say it was a positive in SoulBlazer's case.
From when I played, I recall you could effectively just tank most if not all of bosses in the Japanese version (especially with the bracelets and a herb).
The western release merely boosted them to a mild challenge.
Unless someone wants to do some hacking to restore the bosses to cakewalk difficulty (in the case of the first boss, the difficulty comes from changes to the room layout itself).