Hi,
We currently do not take velocity into consideration when evaluating the density field. As Sam mentions, you can export the velocity data to the Scene Velocity texture by enabling the CVar above. This currently only works when there is another asset that is visibly exporting velocity. Since only one velocity value is written to the channel, this is only viable if the volume is sufficiently dense, acting more like a surface.
Performing correct 3-dimensional sub-frame interpolation would require modifying the material to perform akin to temporal advection on the density value. In the past, I have had successful results when implementing Eulerian Motion Blur to do this advection step: https://diglib.eg.org/items/06146232\-53c9\-4af5\-93c6\-c7746e54341a
The main issue with the technique is the significant cost of evaluating density multiple times within the material. The data access pattern becomes more unpredictable as the velocity magnitude increases, and that has a significant impact on performance.