Japan and Sweden have nowhere near the amount of jets the US has and will ever have in game. Those jets were only used by those nations and no other nations in game. They are important, iconic domestic vehicles.
You overlooked the primary reasoning. All F-5A production was intended for Military Assistance Program [MAP] and export, but the ones the US did take for use (such as the "Skoshi Tiger") were modified and later redesignated as F-5C. Those that were not, were used for training and exercises. So specifically the F-5A variant we have coming is the least applicable t