Seriously. Many ingredients are different depending on if they’re packed, scooped, or sifted. 1 cup of brown sugar can be very different than another cup.
I tried this with cocoa powder before, as I've seen some people in cooking videos shake the cocoa in the cup, and shake the cup to flatten it. And others scoop the cocoa with a spoonand flatten it with the spoon to fill the cup.
The second method yielded over 1.6 times the amount of cocoa powder!