The reason the Mitsubishi SpaceJet failed was that the Japaneses did not understand that you had to start the regulatory process up front with the start of the design and manufacturing. That you could not post design and post production certify things.
It comes from a lack of understanding the regulatory process and with a strong amount of ego that they are experts and know what they are doing.
I've personally dealt with a major Japanese company that made heat exchangers for power plants on a $20 Million in heat exchangers replacement project (with another $20+ million in labor cost to remove the old and install the new ones). They considered that their standards were so much better than the ASME standards that they just crossed out all references to ASME standard and substituted their Japanese standards instead (US Law requires that pressure vessels meet ASME code). They also refused to consider the better tube materials for my application than what I specified - and insisted that their use of 304 SS was the best material for all of our plant's heat exchangers. Japanese Engineers with 40 years of heat exchanger experience had never ever used any other tube materials than 304 SS - and tried to explain why it was superior to everything else out there in the world for my application. 304 SS is great for some things, and quickly fails for other things, and in my case would likely fail from fatigue cracking in 10-15 years (I specified an alloy which would not fatigue crack for well beyond the expected future life of the plant) - which is why there are several dozen different common tube alloys used in heat exchangers in the world (copper, brass, copper nickel, steel, common stainless steels, "super ferritic" stainless steels, to inconel, etc) with multiple grades of each alloy. Needless to say their bid was dropped from the consideration list (and then they requested to know why and tried to explain that their heat exchanger standards were better than the ASME standards, ignoring my pointing out that legally I could only install heat exchangers that met ASME standards).
Such ignorance and ego combined is a dangerous combination for industrial design companies. As I followed the SpaceJet saga... I saw many of the same thought patterns and heard many of the same comments from Mitsubishi engineers and executives. They knew better.... until it was obvious that they did not and could not certify the aircraft without going back and starting over on many things.
It is for the customer to decide what he wants in the proposal. I design FRP tanks, some customers want TP304 SS for the anchor lugs, others want TP316, still others want Hasteloy or Titanium. It's their choice, but those choices affect cost. Quite appropriate to not accept proposals that do not comply.
MHI seemed to be more toward automotive quality standards, not aviation quality. Often it is the difference in traceability, do we know the exact heat of metal has been used with all the test certs on file for that part. It doesn't work in aviation to declare, we have test reports for all our metals purchased and they meet specs. The traceability is there so if there are problems with a part, all parts from that batch of metal can be traced back and removed.
A woman inspector at a Tacoma, WA foundry went to jail because she felt the very cold test temperature (-100F) was silly and was more than the labs freezer could obtain. So she did the test at a higher temperature to be easier. However, with many steel alloys there are a number of different solid phases, the specification wanted to test the worst of the solid phases for brittleness. She falsified over 240 tests over 32 years. It took 25 man-years to investigate whether the parts from the foundry were SUBSAFE.https://news.usni.org/2020/06/19/navy-h ... fraud-casehttps://www.kitsapsun.com/story/news/20 ... 778857001/
Aviation certification works on similar standards, doing something less is non-compliant.