The Oculus support was dropped because their requirements changed drastically:
The DK1 (which was demonstrated with the SkyController) used a single 720p display, which the SkyController was able to drive at a correct frame rate. But version after version, they increased the screen resolution and frame rate, and now the embedded GPU of the SkyController is no longer able to drive properly their screen.
They also require USB3.0 for communication with the headset (SkyController only has USB2.0), so the tracking won't work either.
So all in all, the SkyController is technically unable to drive properly a headset as the Oculus Rift CV1.
The four supported headsets, on the other hand, have manageable screen resolution, and moreover do not require image processing.
In any case, the SkyController have no support for head tracking on these headsets.
Hope this clarifies the issue.