Ur28m S/PDIF setting missing from dspMixFx on iPad

In the dspMixFx on my iPad I am unable to set the routing of the S/PDIF. On my Mac this works fine, but on the iPad the setting to select the output routing is absent. If I set it correctly on my Mac and then import the settings into the app on the iPad it still does not recognize what should be sent over S/PDIF.
Is there something I am missing? Seems to be a bug?