If you’re envisioning a sloppily torn 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.