EEVEE: Discrepancy between multiple and single irradiance volumes

Rendering a given scene using a single irradiance volume lightprobe versus multiple irradiance volume lightprobes (both sampling from the same locations) gives different results. This assumes that no other lightprobes are present, and that the influence area of all lightprobes involved covers the entire area of interest. In the case where there are multiple lightprobes, every single lightprobe covers the entire area of interest in its influence area.

The results of this discrepancy can be seen in the image. The left image shows the render results with multiple lightprobes, while the right image shows the render results with a single lightprobe. Notice the lack of lighting on the ceiling and walls past the columns on the left image, whereas the right image clearly shows lighting on both areas mentioned. Note that in both these renders, there is a single area light in the middle of the field of view, aimed downwards.

Blend files for both scenes are available on request. Besides the aforementioned difference in the number of irradiance volume lightprobes, there are no other differences in the two scenes rendered.