You have a good understanding of why this is the case. Hyper-V would be doing the job of Virtual Box and boot2docker which is what most developers have been using to run Docker daemon on non-linux hosts. I've tried the Hyper-V driver with Docker Machine and had some issues. So I'll be sticking with Virtual Box until that changes.
Is this a surprise?
Containerisation is not magical pixie dust -- it's a particular approach to implementation that is specific to the OS. You have a single kernel, and it follows that in general that single kernel will only allow corresponding containers to be run.
That there will be a Docker server backend that can speak Hyper-V doesn't magically make a Windows kernel into a Linux kernel, or vice versa.