I need to pass some layouts to Calibre to check this. If I read the rules as they are documented, it is not possible to stack the capacitor vias. But I find this very unusual; other processes where I've used stacked MiM caps allowed the vias on top of one another. I drew the diagram based on my experience, and later discovered that when I implemented the rules as specified, I was getting errors, and those errors were consistent with the rules as stated. For the POR circuit, I worked around this by offsetting the capacitors slightly, allowing me to make some use of overlapping, but it's not an ideal layout geometry.