You meant "Super Mario: Yossy Island", right?
As for Mushi, no, that doesn't count as "the official transliteration" to me. The only ones I accept as such are those in the game logos (being an actual part of it, if not its whole), and only because you can't ignore them. Everything else is just "incidental" stuff, which indeed may vary if it happens to be more than one place using romaji.