Nothing about end-to-end latency of the R1 tells you anything about how pipelined it might be. It very well could have multiple frames in-flight at the same time in different stages of processing.
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.