Well, companies in China do have some history of cutting corners and the safety regulation is lower there. So material in China has a greater chance of being not exactly what is on the list, or of having unintentional contamination.
For instance, butylated hydroxy anisol is a molecule forbidden to be used in cosmetics in France because it has certain labeling, but that is not the case in China (and I think the US?). This is just a tiny little difference for one tiny chemical, but where something is manufactured is one thing, where it is destined to be sold is another. Often one factory in germany might manufacure one grade of a chemical for the UK and another less pure one for Russia, even though they are 99.9% similar!