In contast, when instances are chosen to add vividness, the instances are more likely to be vivid and overly specific. 'Kite string'. 'The County Hospital On Thursday'.
A cowboy speaking about men who work with sheep:
I had always let 'em pass, just as you would a jack-rabbit with a polite word and a guess about the weather, but no stopping to swap canteens. (O. Henry)
Whatever the category (which is mostly established by contrast), swapping canteens is not a typical member.
So, the point is that when you include the category, there is still a difference between the instances you would choose for vividness and synecdoche versus the examples you would choose to help describe the category.
They [news reporters] were just diligently doing their job, covering mundane events – funerals and fires and fairs.
Did the author need examples? Not really. The category ('mundane events') was already given, and that category doesn't seem mysterious or difficult. Those examples don't increase understanding of that category enough to be worth including for that purpose.
I think the author wanted vividness. And the point is, when you write you should think about whether you are using examples to communicate the category or for concreteness and vividness.
If the author had been thinking synecdoche, she might have constructed more vivid and specific examples. Such as, at least, county fairs instead of just fairs. (She might have been wanted all three having the same sound, but I doubt that's an important issue in fiction books.)
Honestly, no one cares if we call that synecdoche or not. The only goal is to write better. But, as far as I know, thinking synecdoche helps.
What is a one-sided category?