DirectX 11 feature levels
I've written a program, which uses DirectX 11. When creating the device, I use feature level  9.0c (D3D_FEATURE_LEVEL_9_3, to be specific). 

My initial understanding of feature levels is, that choosing one allows the program to be compatible with graphics cards, which does not support later versions of DirectX.

As far as I know, DirectX 11 may not be installed on Windows Vista (at least not officially), but imagine, how surprised I was, when all graphics features worked like charm on Windows Vista.

The question is: why? How? Is the DirectX 11 so smart, that it uses DirectX 9 binaries, when no 11 ones are available? Is it maybe the feature of DirectX 10? Maybe Microsoft enabled Vista support for DirectX 11? There must be something to it, I don't believe in such coincidences...

MSDN is silent on this matter. Or at least I couldn't find the appropriate topic. 

Any explanation for this?
DirectX 11 feature levels
===

I've written a program, which uses DirectX 11. When creating the device, I use feature level  9.0c (D3D_FEATURE_LEVEL_9_3, to be specific). 

My initial understanding of feature levels is, that choosing one allows the program to be compatible with graphics cards, which does not support later versions of DirectX.

As far as I know, DirectX 11 may not be installed on Windows Vista (at least not officially), but imagine, how surprised I was, when all graphics features worked like charm on Windows Vista.

The question is: why? How? Is the DirectX 11 so smart, that it uses DirectX 9 binaries, when no 11 ones are available? Is it maybe the feature of DirectX 10? Maybe Microsoft enabled Vista support for DirectX 11? There must be something to it, I don't believe in such coincidences...

MSDN is silent on this matter. Or at least I couldn't find the appropriate topic. 

Any explanation for this?