I don't think you can really say "they" did the Halsey thing; it fits the pattern of Karin Traviss' previous works.
After reading K5 trilogy and GOW novels, I don't understand why 343i chose Karen Traviss as the lead writer.
GOW's world is all about tragedy. Human is facing extinction, the main characters' families are either gone or missing, and there isn't any hope to survive at all. This is what Karen is good at, telling how people are struggling between life and death, and the conflict caused by different thoughts.
However, K5 trilogy is about conspiracy and scheme. It is about how ONI uses dirty tricks to keep humanity safe, and it shouldn't involve too much personal feeling. All those insurrectionist father, Halsey is evil, and crippled Spartan things are just childish if you compare that to the survival of human, yet Karen spends like 2/3 of the book telling us about these. I cannot help but keep thinking "This is so sissy" when reading K5 trilogy. Just do your mission, you are f***ing Spartans and ODSTs! Stop mourning your dog and start to save the humanity!
If you are trying to tell a sad story, Karen is a good choice. I really enjoy GOW books. But if you are trying to go big, you shouldn't waste most of your books talking about personal thoughts.