This is a completely hypothetical plane set right?
Not completely, but goodly parts of it are, yes -- I hear you and understand. Reasons why are discussed in detail in the "Reasons for Various Aspects of Rules" section, in the "Aircraft Set Overall" subsection:
"In real life in this period in Burma (late 1941 to early 1942), the Japanese pushed the allied air forces out of Burma. Then the allies came and took it back starting late 1943 and early 1944. In this first period, the IJAF had Ki-21 Sally bombers (60th, 12th, 98th Sentai), Ki-43 Hayabusa fighters (64th Sentai, etc.), Ki-27 Nate fighters, and some other types of lower performance. They didn't have Betties, Zeros or Dinahs. Likewise, the allied forces had P-40B's (AVG 1st, 2nd, and 3rd Sqdn), Hurricane Mk IIa's (RAF 17 and 135 Sqdn and 1 other), and F2A Buffaloes (RAF 67 Sqdn). They didn't have P-40E's, F4F's, Spitfires, or Beaufighters.
Perhaps a mix of aircraft that would be more-historically accurate would be P-40B's, Hurricane Mk I's, and F4F-3's (with 4 guns, as a good fit for the F2A, actually -- see America's Hundred Thousand for a comparison of F2A vs. F4F) for the allied forces (with the ratio of P-40's:Hurris:Buffaloes being 1:1:0.333) and Ju 88's (as the best fit for the Ki-21), A6M2's (for Ki-43's), and D3A's (for Ki-27's) for the Japanese forces (with the ratio of A6M2:D3A being 1:1). However, historically, the IJAF forces drastically outnumbered the allied forces, so if these more-realistic aircraft were used (where IJAF fighters are much worse than allied fighters), we'd also need more-realistic side balance with the IJAF probably having, say, 3-5 times as many players as the allied side. DoK, the original designer, picked more-contemporary aircraft and more-even player numbers. We're keeping it that way (1) because changing as described above would be a major change, requiring redesigning the scoring conditions, experimenting with side balance and playability, etc. and (2) because this scenario is already delayed compared to our originally desired schedule. Maybe in the future version, we'll try a more-historically accurate mix of aircraft."