DC_SUPPORTED == 1 is ok as long as you disable DC at slave from master. i..e select SM sync / FreeRun.
I am not sure SSC is up to date with ETG1020 (EtherCAT Protocol Enhancements). It does not seem to be the case from SSC appnote which I mentioned above and stack source code.
Suggest to post in EtherCAT forum for stack feature related queries. There is no dependency on the firmware for the behavior you are seeing with Object Dictionary structures...