Why does Jarvis not translate all the comments made by the white women about Sibeko's daughter?

In Chapter Twenty-Five, James and Margaret Jarvis visit Barbara Smith, one of Margaret's nieces, on a day on which court is not in session. Margaret and Barbara discuss Ixopo. While Jarvis reads, there is a knock on the door, and he finds Stephen Kumalo there. Kumalo is surprised to see Jarvis, and sits down on the step as if he were ill or starving. Kumalo begins to tremble, and Jarvis believes that he is ill. Jarvis goes to get water for Kumalo, and when he returns Kumalo brings a paper from Sibeko for his daughter, the Smith's servant. Jarvis tells Kumalo that he recognizes him, but he does not know the relationship between them. Kumalo admits that it is a very heavy thing between them, and he is afraid to tell, for it is the heaviest thing of all their years. Kumalo finally admits that it was his son who killed Arthur. Jarvis tells Kumalo that there is no anger in him. The Smith daughter returns, and tells Kumalo that Sibeko's daughter was fired because she started to brew liquor on her room and was sent to jail. She says that she does not know and does not care where the girl is, but when Jarvis translates this to Kumalo in Zulu, he leaves out the fact that she does not care.