Twenty grams is a spoon-scale amount rather than a cup-scale one. For most dry ingredients it lands between one and two tablespoons, which is where a set of measuring spoons serves you better than a cup.
Across the full chart above, this same weight fills 0.24 cups of cocoa powder but only 0.06 cups of honey. Cocoa is the lightest ingredient here and honey the heaviest, and that spread is the whole reason the ingredient has to be named.
Keep the original 20 gram weight whenever the recipe depends on an exact ratio between flour and liquid.