Dwmgoods35 had a point. If you are a reseller on eBay and your wholesale supplier is also selling on eBay, then, it would be a disadvantage to you because you are practically competing with your supplier. However, if the supplier is selling the goods on eBay @ retail and you get your goods from them @ wholesale which means that you can offer competitive prices without losing money, then, that should be okay.
Also, that is one strategy that a seller can apply-sell on other eBay sites to get more views and to target buyers from a certain country. As with Zhenda's store, they are based in Hong Kong but they are also listing their products in eBay UK but as long as the listing states the item location or where it is being shipped from, then, that should be no problem.
Have a great weekend, everyone! :)