I logged an incident with SAP Support "PDM table generation not working for OOM Complex Data Types" (178581 / 2016), and they have raised KBA 2293310 in response (http://service.sap.com/sap/support/notes/2293310).
I'm using PowerDesigner 16.5 SP04 PL01 - not sure if the issue relates to my version specifically, or others. Would be interested to hear from anybody who has got this to work correctly.