I'd love a look round some of these of factories. Personally ive seen a variety of quality of workmanship from at least one of these manufacturers (waltly) that makes me think theres a variation in quality of machine / manufacturing cell or set up or just control.
Im not trying to bash anyone or anything, but personally I'd advise looking into common problems with a brands chosen maker before splashing my cash. After my last issue I didn't convince myself another was worth the outlay.
I'd say that's the point, more so than anything else. Factories with variable QC levels may simply be badly managed in that area at that time. Staff turnover is one thing that should ring alarm bells when you visit a factory a few times.
Most factories are capable of doing a good job but doing it consistently across the range of designs they make - some sound, some seemingly having problems designed in - it's no suprise that materials like Ti and carbon show up the range of quality even within just one factory's output.
Edit to add. Blaming QC can be an easy way out for a brand. I remember an MTB brand that had really high failure rates and they blamed the factory quite publicly. I went to the factory in Taiwan to do some work on a Genesis bike sample, working with the engineer there (was a FS bike and I needed the help of someone who knew what they were doing in that area). He showed me round a few projects and test jigs etc, including a frame from that brand, said it couldn't be made well, but they insisted. He explained why they kept breaking and it all seemed quite logical, said it was clear from sample frame/design stage onward and that they kept ordering them because the basic design couldn't be changed. Felt bad for him as his team were the scapegoat for a brand that thought they were smarter than the guys who have all that production experience. I don't know for sure why those frames broke but they way it was resolved a year or 2 later suggested the factory engineer was correct.