Because the translation is plain wrong. It's not up to the translator, but the context. Tachibana is not questioning his gender or anything, he still identified as a man no matter how he looks, so this is just a failed attempt at inclusivity.
Seeing karel's smile before the war and how sweet and loving he was versus him after the war is so heartbreaking, the war and Sasya's abandonment really broke this man
First time having sex with him and Mephisto already broke him