Wow. Every picture of chrona is tagged as androgynous but none of them are tagged as trap or reverse trap. We really don't know which one chrona is do we?
I've never seen the series, but just on my knowledge of translations, I wouldn't put much stock in that. While gender-specific pronouns do exist in Japanese, they're actually very rarely used; for that matter, second- or third-person pronouns in general are in the same boat. By contrast, it's extremely difficult to form a cogent sentence in English without them. So, I'd be willing to bet good money that the original Japanese dialogue never makes any mention of Chrona's gender, and the "he"s you heard (or read, rather) were added by the subbers out of necessity.