Here is another note from later in that log that seem to be relevant:
Change 3346526 on 2017/03/14 by .
[Copy] Volumetric Fog supports point and spot light shadows
* These lights are injected separately so that per-light resources can be bound (shadow depth map, static shadow depth map)
* Forward lighting of local lights can be forced with 'r.VolumetricFog.InjectShadowedLightsSeparately 0'
* Shadowed lights come at a cost: 2.9ms for volumetric fog on 970 -> 4.2ms with shadowing