Is it the same? A cup of liquid versus a cup of flour?

Hi, I was making daifuku with a bunch of friends one day, and we ran into a problem. None of us are kitchen savvy, but we really wanted to make daifuku and we thought it would be fun. Anyway, we ran into the conundrum that we needed a cup of rice powder. All we could find was a 2 cup container that was for liquids. They wanted to fill it up half way and just use that. But I argued that if we did that it would mess up the recipe, because I thought that using the two different containers would give us slightly different measurements leading to too much rice powder. My question is would it really have been the same amount had we used the one cup that usually measures liquid versus the one cup that usually measures things like flour?