I might have read that wrong, but it seems that the reference design is ultimately the blueprint for existing WP8 devices, specifying the exact ingredients (possible solutions for chipsets, etc) needed in order to pass certification. They're just taking their process of working with vendors to build these devices and basically open sourcing it so that newer manufacturers can ramp up production faster.

What made you think it had to do with the rumored Surface Phone? If anything, the mention of other smartphone vendors sort of negates that claim.