Inquiry on generating Aircraft and Officer ratings

[atheory]

I'm curious if any knowledgeable enthusiasts out there could share some insights on how one might go about generating various stats, or ratings, for aircraft and or officers/Generals.

I'm not looking for a definitive formula nor debate as to which game uses the best or which are most accurate. Only attempting for myself to understand such systems and how such ratings are generated.

For instance, WitP has an aggressive rating for their generals/admirals. How do they determine those numbers? Is it a formula or just an educated guess. HOI IV gives its generals a level scheme of 1 to 5, with 5 being known stars like Rommel, Guderian....but for all the lesser known generals that are only levels 1 to 3, how is it determined who gets what level? And War in the East has no less than 8 ratings for its leaders, (Political, Morale, Initiative, Admin, Mech, Infantry, Air and Naval). Again, how would such ratings be determined?

The same could be applied to Aircraft....I come at this only from a 2D hex turn-base style gameplay. Typical ratings one would find are for fire power, maneuver, endurance and armor. I would assume here there are more concrete formulas at play, and while dogfighting or determining which fighter is better than the other is subjective and ultimately leads to the phrase "it all depends". But, there is obviously an approach that games use to skip beyond that noise and come up with something concrete, whether it be somewhat realistic or abstracted enough for gameplay purposes. It is here, understanding how its generated for gameplay purposes in a 2D hex turn base game, that I am most interested in truly understanding.

Thanks in advance for any that take the time to consider a response
Respectfully
Atheory