Well, I'm not going to engage with this any further really. But HMMA built the Theta II in Alabama and for the 2015 model year they built two different versions, the updated version for the 2015 sonata and the old version for the optima and sorento and by MY2016 failures have been a lot less, which coincides when HMMA started building only the updated version. Hyundai is very controlling of their suppliers, more so than most automakers, Hyundai Mobis controls everything on their watch, they are in total control of nearly every process. With Hyundai being very tight lipped about the engine failure fiasco and their original stance that manufacturing debris caused the failures, I wouldn't put anything past them.
My work is in the automotive consulting business. I work with auto manufacturers on finding ways to reduce business costs, my area of expertise is strictly regarding vehicle exteriors. Parts can change upon a moments notice while on the assembly line. When the 2013 Accord, Altima, and Sentra came standard with chrome exterior door handles, that was a requested cost cutting measure requested by the OEM's. Also after the tsunami of 2011 the Japanese makers were looking for ways to use less paint coating. Not having to paint door handles for several different colors and just using chrome across the trim levels saved them money in the long run.
Anyway, from how I see things, it looks like Hyundai/Kia got a handle on their engine issue by 2016 for the most part. My very educated guess is that 2017+MY's have a failure rate that is acceptable by industry OEM industry standards. At that point all the suppliers had converted to producing parts for the "updated" engines.