As do most of supplement companies? Even the giants like NOW Foods, Swanson, Vitacost, Doctors Best, Source Naturals and so on. China is very cost effective.
The difference I find is that very few companies bother to have the stuff tested before reselling it. For example, where as NOW Foods have their own in-house lab and staff of trained chemists doing QA on all raw materials, I've found that for some products Swanson relies on Chinese and Indian manufactuer CoAs.
PowderCity have every batch tested after they receive it from their suppliers and before it goes on sale. They use Colmaric Analyticals (located in Tennessee) to obtain purity, bacterial count and heavy metal testing. I've requested a few original certificates of analysis from them and it checks out as far as batch numbers matching the products I've received.
I'm not sure what your point is with that FDA link. Many supplement companies were sent a notice advising that AMP Citrate was not being recognised by the FDA as a dietary supplement (i.e. not something found in the human diet or herbal or derived there-of). AMP Citrate was a popular preworkout ingredient that replaced DMAA after sites and preworkout products started to withdraw it from sale for the same reason. Powdercity sold independently tested AMP Citrate and then ceased selling it.
Also, I won't name names but I've seen a few supplement/nootropic companies/ebay sellers mentioned on longecity that also source from China but do not have an open and honest practice of testing before on-selling, saying "trust me, it's pure, I tried it" or saying "trust me, no one has complained" or "we are experts, trust us" etc.
Each to their own, but I think people should be more careful.