It could be that they did work with the original creator with this and the original creator allowed it to happen, too. Sometimes they'll add lines to add clarity in English or remove lines that English speakers don't need. Like how English Voice Actors who dub an anime will often add lines and change things because a straight 1-1 translation of a language is just boondoggles. So they really are trusting that the translator is imitating the voice that the creator would have had if they were creating for an English audience to begin with. And, that is probably why they also went with the choice to change ages and context if they felt like it wouldn't vibe with English speaking audiences.
Kind of annoying when they change names into western names, or tell me in an asterisk what Kimchi is because they assume I'm too isolated to know that. Like there's been quite a few comics I had to put down becuase the translation sucked, but it's hard to say if this is something that the creator doesn't know about.