The beta ownership API returns role, access profile, source and application owners. However, I do not see anything being returned for governance groups or policies or anything else. Is this something that will be enhanced or is it a bug?
Update- I opened a support ticket and the reply was not encouraging. There are no plans to make enhancements to include other owned objects at this time. I hope the API doc is updated to reflect the specific objects returned. This is an odd gap.