The phenomenon occurs even if mobileHDR is turned off.
Also for Instanced Stereo, whether it’s on or off.
After testing with various patterns, I may have noticed the cause.
With MMV off, using MSAA seems to make my left eye black.
It seems that mobileHDR and InstacedStereo have nothing to do with each other.
Switching to FXAA fixed it.
With FXAA, even with MMV off and InstancedStereo and mobileHDR on, the left eye didn’t turn black.
But my research is not very reliable, so I think it would be better for you to do a thorough research.