SerialSlayer The difference in damage is not fictional. Set up a personal challenge, or, if you're afraid challenges are bugged (even though they aren't in that regard), you can also test it in MP. Simply set a howitzer near a wonder that's on the edge of the map (there are always these). Once without fury, once with fury, also the 2 players you attack need to be of the same age (that way every wonder has the same hp, hp of wonders is dependent on age). Also prefereble to attack below Atomic, they might have that library research that boosts wonders hp.
You'll see for yourself, fury attack will visibly result in your howitzer doing more damage than without fury.
As for the way they set it up, who knows. All we know is that axes appear above all affected units once they are deployed to battle (and it's really everything, regular troops, mercs, planes, etc.) and they do more damage.