Those 12ms affect the latency, not the framerate. The thing will definitely not render at just 60Hz as that's too low for VR, the standard is usually 90Hz or 120Hz.
That's why I assume the R1 is trying to provide the render pipeline with "current" positional state and then tries to finish the drawing in the remaining 4ms (for 60fps) then the display is only going to lag the wearer's perception by 16ms which is less likely to cause discomfort.
This could be mitigated more if the objects in the VR scene are tagged with motion vectors. If the R1 state update doesn't land in time the renderer can interpolate the "current" position by applying those motion vectors to objects in the scene.
Not even the most expensive high-end gaming setups can finish the entire input-to-screen processing within just one frame, and yet they can easily render some games at 500Hz or more.