When I read chapter 13 and found grammar error, I thought it was just a typo. But why does the Typo continue to chapter 14?

Why are there so many grammatical errors in the last two chapters? As in the first paragraph of chapter 14. It says "No, young master. He is the son of the maid of this house. His name is Biyan". Actually, Biyan is a boy or a girl? From chapters 1-12 Biyan is told as a girl. But why do chapters 13 and 14 say Biyan is a man? Biyan is a daughter not a son. It should have said, "She is the daughter of the maid of this house. Her name is Biyan." Recognize the difference of He and She. His and Her. It's importantant cause if it's wrong it will confuse and complicate the reader. Especially if there is an introduction to a new character and the dialogue is "His name" even though the character is a woman