Karnak you are right and I stand corrected. "As designed" needs to be clarified, as you pointed out, since there are several states of that.
There is as originally designed on paper before production. Then there is flight testing where it was seen if the plane performed up to specs or not. Ultimately leading to operational release with defined specs for use in various arenas. And I am sure I am leaving somethings out.
So yes, you are right AH models its plane on operational specs. However, AH does not model its plane differently depending on theater, environmental conditions, uneven production quality, uneven material quality, level of maintenance, quality of maintenance, availability of spare parts, accumulate flight hours. It also doesn't model the pilot fatigue or pilot state of health and affects on plane performance in combat (well besides wounds .. a fatigued or pilot who doesn't feel well will generally not perform as well as that one who is rested and healthy irregardless of the machine he is flying) which was a factor in several arenas which suffered from a lack of pilots and replacement pilots.