Hi Ali124,
The second part of your post suggests you may have read the question stem incorrectly. You wrote:
I chose (A) instead thinking author of Psg A agrees while author of Psg B disagrees, but upon second look, I think we don't know what author of Psg A thinks about (A).
But, the question stem asks for an answer choice that BOTH the authors would disagree with. (Your comment suggests you were trying to answer a question more like "Which statement would the authors disagree about?")
At any rate, I agree with you that we don't really know what the author of passage A would think about the statement in choice (A).
As for answer choice (E), you said in your comment that you understood passage A as saying, in line 21, that "even if readers notice a lie, that [they] will not hold the author against it." I agree with you, so the author of passage A would disagree with the statement in (E).
My guess is that you read the passages perfectly but made your mistake when reading the question stem! Please follow up with more questions if you're still fuzzy on this.
Thanks for the question!