Powdered sugar: fine particles change behavior

Useful to know

King Arthur distinguishes powdered sugar from granulated sugar by particle size and use. Powdered sugar also often contains an anti-caking starch. The absence of large crystals changes how it behaves when creamed with butter. [1]

That can be useful for icing but affects a recipe that relies on sugar crystals for aeration. Compare by mass where the recipe provides that basis, rather than substituting equal cups. Read the actual product’s ingredients. Similar sweetness does not mean the same structural role.