Is this something that will be improved or is it going to be a lasting limitation of Lumen?
The issue seems to occur very reliably when lights are placed within ~20cm of surfaces. Making it difficult to get good results out of volumetric scattering from lightsources as the light needs to be placed too far from the emission source to make visual sense:
Using the r.LumenScene.DirectLighting.ForceShadowMaps 1 resolves the issue, but I have to assume there is a tradeoff being made there, or it would have just been enabled by default.