Yeah, the use of "he", was entirely a translation thing. The official english translation handles this better, and tbh is kinda a bit better in general, not to hate on hachimitsu, they do great work, but in this instance, the official translation beats it out.
Edit: Hachimitsu did stop using he/him as well though, so I don't really know where this person is coming from saying everyone misgenders Mogumo.
I think this is ultimately just another case where the translators had to wing it and once it was clear that they got it wrong, they correct it. Not uncommon in fan TL - the popular fan translation of Dangan Ronpa messed this up since they had no way to know (because it was a plot twist). Hachimitsu is pretty thoughtful about this in general when they do have enough information
The official TL will often have access to notes from the author so they were able to get it right - that's another upside to official translations even if the scans sometimes do a better job with tone or nuance.
It's a tricky balance though. Sometimes misgendering the character is an accurate representation of the dialogue even if it's uncomfortable to read.
Speaking of uncomfortable to read... as a big fan of this series I feel like the last two chapters have been a bit too much. I kind of understand what the author is going for here but I hope this doesn't become the new tone of the series from here forward, it's kind of dropping a bunch of different familial and personal issues on the reader at once along with sensitive issues like suicide and abuse. It feels like it would've been better to spread it across a couple more chapters, though they at least introduced the eating disorder stuff more slowly.
IMO Bokura no Hentai is a good example of dropping these themes on the reader a bit more slowly and incrementally, though the sexual assault themes still kind of slap you in the face with little warning. I do think fukaboku is doing a very good job of making each cast member distinct and relatable, better than most recent series in the genre.
