I think the biggest difference is in rough v. finished (ie fished) work.
With the former, while having a few inches of slack isn't a bad idea, it can result in an "unworkmanlike" appearance that might peeve AHJ's during a rough inspection.
With fished, who's going to know?
![[Linked Image]](https://www.electrical-contractor.net/ubb/wink.gif)
(just kidding)
Maybe the goal is to anticipate future access to the wall cavity. After all, most folks think of wire going pretty much perpendicularly out of a box.