As far as I know MSFS doesn't use real reflective textures either, just a gloss map on the Alpha Channel, offering in FSX either reflective or specular shine. That is far better than what CoD currently provides but still not a true reflective texture. A true reflective texture would actually reflect the scenery visible from the surface reflecting (you should be able to "see your face in it" so to speak). Note I don't paint for MSFS so I could be wrong, though I would be surprised. If you can fly alongside another aircraft in FSX and see your own aircraft reflected in the bare metal of the other one it has true reflective textures.
Even the MSFS Alpha Channel "specular shine"and reflective textures can really suck up your FPS.
In an ideal world you could turn on reflective textures as an option specifically for the use of the occasional person with a sufficiently high spec machine.
In the real world, the forums would be flooded by FPS complaints from people with old hardware (who should have had more sense than to even consider trying reflective textures) demanding it be "fixed" right now. I suspect its politically safer to leave the feature disabled for quite some time
The IL2 way of doing it does work ( I used the technique to good effect on my IL2_1946 prewar gladiators) ... but its not just cutting and pasting in some nice blue tinted reflections, it requires detailed work with multiple layers and an understanding of lighting and how it relates to the aircraft in question.