Dave is half correct.
We did throw away our old, terrible OpenGL renderer several versions ago.
But we also do still use OpenGL in various places where it makes sense, as described here:
GPU (CUDA, OpenGL) features in After Effects
The reason that After Effects shows OpenGL 2 in the GPU information box is because that is the version that is being used for these features. When the application starts, it tells the OpenGL system what level of features it needs. We're not using any of the more advanced features of OpenGL 3 and later yet.