OData 8.0.6 and older Navigational Property in Complex Type as returned value on Post + Action not expanded or returned.

Example usage,

var extractSensitivityLabel = builder.EntityType<v2.SensitivityLabel>().Collection.Action("extractContentLabel");
            builder.ComplexType<v2.ContentLabel>().HasRequired(c => c.SensitivityLabel).HasAutoExpand();
            extractSensitivityLabel.Parameter<ContentInfo>("contentInfo").Required();
            extractSensitivityLabel.Returns<v2.ContentLabel>();

Debugging odata showed that WriteExpandedNavigationPropertiesAsync failed to write the property due to the fact that
CreateNavigationLink failed as the writeContext.NavigationSource == null in this case.
it was set as null as the segment.EntitySet == null.
If this is by design unsupported please document, as this works well when its a HttpGet request from a Function but then parsing body information has different issues.