Actually, for this series, they redrew a lot of SFX. Not always, but often.
Official don't redraw SFX at all. They just add a small side text.
Scanlators go beyond what official cares to do.
You make it a simpler matter than it actually is. I, as I'm sure many other people too, don't want to see SFX redrawn. They're part of the original art, not just something superimposed. It's over-localization and usually it also results in more of the page being covered up by necessity. Side text is the way to go.
I'm a fan of the Yen Press house style, where the sound effect is labeled with a transliteration of the sound in Japanese, with English in parenthesis describing what the sound is. Ex "doki doki (heartbeat)". It's educational! :)
