It gives it an out-of-universe perspective, which is different than having out-of-universe information. Out-of-universe material is stuff like sales figures, merchandise, reception, etc. Out-of-universe perspective is how it's written, in addition to having sections of out-of-universe information.
Sales figures etc are what I would call non-fiction information. Fiction and non-fiction are standard terms for exactly the thing you are referring to - why use some made up terminology for them?