Tag - quality of bags

Lad dips approving helps to quality of bag?

Why does approving lad dips not help to control quality of bag? Quality of bag is by colour, design, material and makes I do not know why some customers require to approve lab dips to control colour quality of bag? Because most lab dips are without any finishing. Even if customer has select the best colour among the lab dips, it surely will change a lot after waterproof finish and pvc coating finish. It causes confusion, as well as cost time(I think usually the factory cost...