It seems to depend on both the MSC and the type of client being shopped. My biggest MSC client requires narratives that add information not in the short-answer questions and that tell a story to make the end client feel as if they're "in the room" with the shopper. Even then, the narratives aren't that long. I did an investment shop that paid a large fee, and the narratives were very lengthy--but I could understand why.
Then sometimes you have shops that you don't feel as if the amount of narrative required is warranted, but you may not know exactly what the end client is looking for. And sometimes I wish I could add narrative to shops that don't address the possible scenarios a shopper could encounter.
I do feel, though, that there are shops where your short, in-the-box answers are sufficient and am not sure why more narrative is needed; it seems very redundant in many cases.
I learn something new every day, but not everyday!
I've learned to never trust spell-check or my phone's auto-fill feature.