Just because every bit of writing is a choice, that doesn't mean the author him- or herself fully understood why they made that choice. We're all shaped by our own life experiences, our family, the time in which we grew up, etc. Often, it's easier for a third party to connect those dots. That's why coaching and therapy works, for instance.

That said, when we're talking about standardized tests, they tend to (and should be) sticking to pretty well-understood and obvious examples of this sort of thing.

And of course, sometimes they're just not well done. Standardized test writers face the same challenges as every other writer, and I think we can guess that the very best writers probably do not end up in that job...