Blue Dragon's translation gets kinda shitty in the last quarter or so. Well, there are only a few places where it's really terrible, but I don't understand how anyone rubberstamped some of the stuff towards the end. I wouldn't be surprised if someone else finished it or something.
And demi, stylistic is probably not the best descriptor, but I do think the slowdown is intentional. It only happens during those spell effects, and it definitely seems like it is a tension/drama thing.
Either way, technical or not, it doesn't have any real effect on gameplay. Don't write it off because it slows down very briefly during spell effects. Write it off because it's kinda dated and the FFT you played so many years ago that is alive in your memories isn't quite as good as the real thing. Get Disgaea if you can only get one SRPG!