I would say considering every action you take has en effect on the world, much less the enormous amounts of content, features, and way more than likely some alternate graphical templates (Ala phasing possibly) to reflect those actions, it's going to be quite a bit from an asset perspective.
Also someone may have read a spec on a box. Last time this happened CoDWW2 was supposed to require 80gb minimum, and turned out install size was 56gb.
Regardless, anyone who doesn't have an external (At least 2tb) drive cannot call themselves true gamers and should go to their local microcenter/hop online on amazon to quit being so awful.