But that's exactly what khim and me is telling. Good switchable GPUs are a hard task to implement.
So vendors simply don't bother with Linux where it'll be useful only for a fraction of 1% of their users. NVidia hasn't even ported their Optimus technology to Linux in proprietary drivers.
In the area of switchable GPUs all we get is airled. And while he's a mega-super-developer, he can only do so much.