The testing agencies only test a sample, not every one. This is true of any fitting (unless it is going into something like the space station or a satellite). The variation of quality seems to be greater on stuff from China, but it's hard to say if you'd ever have a problem or not. On some of those I've seen, the variation in thread quality can be great...they tend to not sharpen their taps and dies often enough resulting in torn threads, or incorrect tapers or depths making it possible to bottom out a fitting before it gets tight or to get a good seal. If it was all installed and tested without leaks, you're probably okay. It's a major pain to build up a threaded system and when testing or in use find a fitting that has a pin-hole leak or a crack in it. Sometimes, I wonder about the economy of the parts used verses the labor and liability involved if there's a problem.