The japanese language is composed of sounds.
the sounds are: a i u e o ka ki ku ke ko ta chi tsu te to na ni nu etc
The only "consonant" that's alone is "n".
When they transcribe words from other languages they don't look at how it's written, they listen to how it sounds.
When you say bomber, you actually say BOMBAR, you even drop the R.
So in japanese you get bonba- ボンバー, the "n" because there's no "m". Or was it bomuba-?
tl;dr you're wrong, it's bomber. the translation in the game is not official.