Sure, 1 Cup is a decent measure for water, chicken stock, or other liquids. After that, it starts to get progressively worse as a measuring device. It can even be okay for fine grain solids such as sugar and table salt, though sugar and salt can vary widely in grain size making this a less than perfect measuring method. But for dried beans or basil or potatoes, a cup is a faulty-at-best measuring device. The less uniform an ingredient becomes, the less likely sized-based measurements work.
All 3 of these piles of basil were “loosely packed” in the same measuring cup. Which one is accurate? How much will the recipe change based on these widely varying amounts?
Instead, a much more accurate measurement is weight. A pound (or 453 grams) of beans or potatoes is very easy and accurate to measure. Admittedly, herbs like basil are hard to measure by weight because they don’t weigh that much so having a scale that is accurate at small weights is important and definitely more accurate that loosely packed.