It figures that's Tanner's logic makes sense to you. Especially since she's what you're not, a civil polite intelligent anti-Mormon that doesn't usually lie to make a point.First, this poetic style has always been in the Bible. Whether anyone had a name for it or not is beside the point; the style was present for Joseph Smith to imitate.
Next, she does a bit of a twist in her statement. Smith couldn't imitate the existence of a specific type of writing in all the right places if he knew nothing about it. Tanner doesn't mention that fact. That's called deception by purpose.
What Tanner doesn't tell you is someone that doesn't know what their copying, they'll reword it in all the wrong places and maybe a few right places because they don't know what their re-writing as Smith is accused of doing.
Therefore it's a fact that Smith in rewriting a specific undiscovered type of writing, he would have massacred it over and over. Those later recognizing Chiasmus, they would have been able to read Smith's book and could point to where he destroyed what should have been Chiasmus and where he unknowingly wrote out chiasmus correctly.
But it's been noted that Smith rewrote Chiasmus as correctly as it was written into the OT without knowing it. Tanner doesn't go over that fact because she can't explain it herself. So it's easier for Tanner to just excuse it away with Smith got lucky in that he didn't slaughter any Chiasmus in rewriting it in the BOM.