The chorus in a play, like a narrator in a novel, introduces a point of view not tied to any of the characters, and both chorus and narrator allow the author to comment on the characters' actions and to introduce information about the context in which these actions take place.
Conclusion
The chorus in a play is not equivalent to the narrator in a novel.
Evidence (since)
The information introduced by the chorus in a play is sometimes inconsistent with the rest of the information in th eplay.
Evaluate
This argument is pretty sparse. It's mostly background until we hit the however pivot, and then the author says,
Okay, so what's being assumed in that case?
The author is Assuming a Difference. If she's saying, , she must think that "Y does not do thing A".
If I said, , I would be assuming that "Karen doesn't own a Lebron jersey" (among other things).
The author said,
Goal
So let's look for an answer saying, .