GetXmlDocsSummary is not working for inheritance across multiple projects

[XamReruam]

The GetXmlDocsSummary method currently does not return a value for properties inherited from classes of other projects

A simple example:
Project A

public class MainTest
    {
        public static void Main() {
            foreach (PropertyInfo prop in typeof(ChildClass).GetProperties())
            {
                Console.WriteLine("Name: " + prop.Name);
                Console.WriteLine("Summary: " + prop.GetXmlDocsSummary());
            }
        }
    }

public class ChildClass : ParentClass { }

Project B

public class ParentClass
    {
        /// <summary>
        /// This summary will not be shown
        /// </summary>
        public string Value { get; set; }
    }

Output:
Name: Value
Summary:

[RicoSuter]

Is this failing because XML Docs of referenced projects is missing in the output directory?