GearVR Sawtooth Wave in GPU Profiler (VR Samples)

For the GearVR Innovator Edition and S6 I'm noticing a weird pattern for Unity VR Samples project's GPU Profile:

(Shooter 180)​

The GPU Usage's - specifically the Opaque component's - pattern is a positive sawtooth wave with a period of 5-6 frames. Consistently 2 frames after the peak the CPU sees an ~30ms frame spike caused by OculusWaitForGPU.

In the above image Clear is the cause of ~99.6% of the GPU time, but if the main camera has Clear Flags set to Don't Clear then Mesh.DrawVBO takes on the same behaviour.

When VR Virtual Reality Supported is set false in the Player Settings the GPU Usage sits around 0.1ms.

Anyone else see a similar pattern? I've seen this in more than a couple projects I've build for GearVR.

 

This page with its train analogy will do a better job than me at explaining what's going on.
Sadly, understanding the situation and knowing what to fix are two very different things ....