The source language in question is Standard Chinese. It is a gender-neutral language. One big thing that English speakers complain about English is the gendered pronoun, namely the third person singular pronoun. In contrast, Chinese does not use pronouns as heavily as English speakers. Sometimes, pronouns may be inserted to indicate emphasis on possession, but it's completely fine to remove the pronoun altogether. When a Chinese text does use pronouns, the pronoun may be 他/她/它 (pronounced identically as Ta), but historically, in literature, 他 was not used to indicate gender, and 他 also means "other", as in 其他.
There are ways to convey gender. One way is to use Chinese kinship terms, but this is only relevant in specific circumstances. Another way is to directly ask the person in the conversation about the sex/gender of the person, because 他/她/它 are all pronounced the same. And another way is to assume a gender for the unknown person. As part of the Chinese Internet culture, some people may use TA, because 他 is too masculine, 她 definitely implies the feminine, and 它 implies an object. Aside from that, Chinese is the most gender-neutral language in the world since antiquity.
How does one indicate the gender-neutrality of Chinese with English dialogue? There is the English singular they, but English speakers seem to use it for a specific purpose - to indicate that the gender of the person is irrelevant, unknown, or that person's chosen gender. But the listener usually does not assume gender at that point, probably because it's culturally accepted that "they" is the gender-neutral pronoun. Chinese, on the other hand, works a bit differently. Even though the listener hears TA, the listener may actually assume male or hold no such assumptions but then directly ask the other person about this unknown person's gender.
The author cannot simply ignore it either. Sometimes, writing English naturally means you have to think in English and insert in pronouns that would have been left out in Chinese. These pronouns indicate gender. The Chinese language not only allows removing pronouns, but also the entire subject from a sentence; and Korean and Japanese also do this. So, as a result, the Chinese-language writer can easily write a whole paragraph without a single gendered pronoun. Meanwhile, the English-language writer has to insert some kind of pronoun (he/she/it/they).