If you’re envisioning a sloppily torn scrap of paper with “KILL EVERY1” scrawled on it with crayon, I could see where you’re coming from, but paper battle maps with points of interest/focus being used by a pretty primitive (comparable to who they’re up against) fighting force makes more sense, though.
If this was planned so tightly that they didn’t let the bulk of their fighters (or large swaths of lower rung leadership) know details until days (or less) before the attack, then it stands to reason they’d hand out infosheets. That seems to be what happened here.
I can’t remember what it was specifically, but friend basically ruined a major plot point in Witcher 3 for me fully knowing I was a good ways out from discovering it on my own. As a kneejerk reaction and knowing he was about 20 or 30 hours into Fallout 4, I told him who runs the Institute and what relation that individual has to the protagonist.
He was angrier than I was because I had assumed Witcher 3 turned out the way he revealed, but my spoiler absolutely blindsided him. He never ruined anything for me again.