Volume rendering multiblock datasets with 3D uniform grids

Release notes for 5.9.0 advertized the fact that one could volume render an MB dataset made of only vtkImageData. (I could never make this work).
I am now testing this with 5.10.0-RC1, and I can’t make it happen either. I created a single “Fast Uniform Grid”, which I wrapped both with a “Convert to MultiBlock” and a “Convert to PartitionedDataSetCollection”. In both cases, I get an error Can not execute simple algorithm vtkImageVolumeRepresentation without output ports
Am not sure if this should work with 5.9 or 5.10?
Thanks in advance for the help