Depends on who you buy it from...and how diligent you are in checking. Sometimes you pay for Swiss and you get ETA clone...complain, send the watch back, and odds are good you'll ge the right one.
I'm not so sure that most of the collectors know the difference visually...they aren't watch experts...so even if it went through QC/QA, it would pass through. They likely take the word of their factories...which are factories engaged in an illegal business, so take their "word" with a grain of salt.
Chris did a photo comparison in his section of how he QCs the difference and ensures you get the right movement you paid for.