The misconception is that alot of people probably don't realise that OGL is being used as opposed to DX without them knowing, as per the list i pasted .
The fact IL2 allows you to choose DX or OGL is just another setting amongst many user are allowed to change in the settings, most modern games wont allow such a vast amount of "direct" adjustments.
The original IL2 was able to run on 8mb graphics and low system spec and with the progression of hardware it soon caught up with the game engine and what IL2 could look like.
Modern games can throw you out of the set up because your graphics/system isnt up to spec (BF2) as happened to my son.
Edit>
After testing IL2 1946 under DX & OGL with IL2 1946 there are many differences with Nvidea cards and drivers, landscape and water being the major ones. "ATI" I cant comment on as I don't use them.
