Thirty grams is exactly a quarter cup of all-purpose flour, which is why it turns up so often in scaled-down recipes. For denser ingredients the same weight barely covers the bottom of a quarter-cup measure.
Across the full chart above, this same weight fills 0.36 cups of cocoa powder but only 0.09 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 30 gram weight whenever the recipe depends on an exact ratio between flour and liquid.