when making leather, I will use creative mode to "trade" hides of different sizes for all medium hides so I can make a full batch of leather. I just think of it as cutting them up since this honestly should be interchangeable.
In my view, it would make sense if they added a step where the raw hides were cut up to form "scrap hides" or something as a step so that the different sizes would become interchangeable. Can keep ratios the same, where small hides become one, medium 2, etc.