If I really want my child to remember a passage, I require this type of narration (rather than a drawn, creative narration, or something else) because not all narrations are equal. Some forms require greater mental work than others, cementing the passage deeper into a child's mind. Generally, our history readings are narrated in this way because I think they are extremely important.
Whenever I ask for an oral narration from a young child, I don't specify what kind I want (detailed or summary). I have found that my child just needs to tell back in her own way for awhile until she is really comfortable narrating. I do, however, correct the 'ums' and any gross inaccuracies after she narrates. If she happens to enjoy giving very detailed narrations, I will warn her ahead of time that I will stop her in the middle of the narration. "...although it is a secret. You will not know when it will happen, so just keep narrating until I say, 'stop.'" So, detailed narrations don't have to have a tidy ending (and I don't have to listen to a huge epistle :- ).
You are probably already familiar with the bead technique (I did not come up with this idea), but I think I should mention it just in case it is new to someone. I like this idea so much. It is wildly popular in our homeschool. If you have two or more children narrating from the same book (maybe mom is reading aloud or both kids are on the same level), then you can give them a small bead of their favorite color. Put them behind your back and have a child choose a hand; whatever color is revealed, that bead's owner narrates for a few minutes until mom says stop. If mom continues reading the passage, or a new passage is read, again, the beads go behind mom's back and a child chooses. If it falls upon the same child who narrated before, then so be it. Never knowing who will narrate is what makes the children very attentive and the game so attractive.
one step at a time...