Why the netcode issue exists, and why it cannot be fixed.

[Hyrist]

Yes, it would also explain the lack of foresight into the potential gravity of the issue as the majority (if not all) of the QA testing was performed on said small country

This doesn't make sense to me.

QA testing could easily be done by Square Enix Headquarters USA, which is located in California, and more than likely was. Granted, this is California to Japan up until the later Beta testing. However I wouldn't go so far as to presume that they did not test, at least in the mid stages, the connection quality of the netcode outside of region.

How their connections would be solid while others are having difficulties, I cannot know. Perhaps this issue did not articulate itself gravely until stress tests began, which at that point it would be too late. But this is all just speculation on my end.