ولا في الجلود عددا
Translation: Nor is salam in hides by number permissible.
The objection to hides counted by number is not merely that hides come from animals. Individual skins may vary in area, thickness, quality and defects; agreeing on 20 skins alone can leave a serious uncertainty about what is owed.
Quduri's wording specifically rejects a salam arrangement based on the number of hides. That limited wording should not be expanded into a claim about every possible transaction in processed hides under every alternative measurement system.