required xmlresolver dependency

Say, before the mailing list goes away, is there a quick summary
available of how the org.xmlresolver external dependency compares
to the XML Catalog API that was added directly to Java for Java 9
(which also describes itself as an OASIS XML Catalogs 1.1
implementation)?

https://docs.oracle.com/javase/9/core/xml-catalog-api1.htm

Does Saxon make heavy use of any specific feature the org.xmlresolver
implementation has that the Java implementation lacks?

Is there anything to report on what happens when Saxon 11.1.1 is used
in an application that is using the Java API?

Regards,
-Chap