There seems to be a bit of a double standard there. People will argue that all sorts of variants are needed, but it seems the legitimacy of the need for variants depends on nationality. If it is German, then by all means the Bf109E-7 is a crucial addition as it allows the Bf109E-4 performance with a drop tank or a bomb, but a Japanese fighter that adds 30mph over its predecessor, nah, that isn't needed at all as it isn't significant enough. US, German and British stuff is treated differently than Russian, Italian and Japanese stuff.
Now, this is only in reference to the players, HTC is limited by the data availability and for them, I am sure, it is easier to get the data needed for American, German and British aircraft.