This is partly to report a packaging bug (or mistake) and partly to ask a question.
partitionmanager3 needs kpmcore3 and does have the dependency for it.
partitionmanager needs kpmcore (4!) yet that package does not get installed if you replace partitionmanager3 with partitionmanager.
kpmcore3 should NOT satisfy the dependency kpmcore!
Next question is: why is partitionmanager3 installed by default instead of partitionmanager? It seems to me as if it the UI is even run as root (as the user theme is not applied), which is AFAIK not the case anymore with partitionmanager 4.