Type change by restriction not implemented properly in Java API

<?xml version="1.0" encoding="UTF-8"?>
<xs:schema targetNamespace="http://openuri.org/easypo"
 xmlns:po="http://openuri.org/easypo"
 xmlns:xs="http://www.w3.org/2001/XMLSchema"
 elementFormDefault="qualified">

<xs:simpleType name="addressType">
 <xs:restriction base="xs:string"/>
</xs:simpleType>

<xs:simpleType name="specialAddressType">
 <xs:restriction base="po:addressType"/>
</xs:simpleType>

<xs:complexType name="customer">
 <xs:sequence>
  <xs:element name="name" type="xs:string"/>
  <xs:element name="address" type="po:addressType"/>
 </xs:sequence>
</xs:complexType>

<xs:complexType name="specialCustomer">
 <xs:complexContent>
  <xs:restriction base="po:customer">
   <xs:sequence>
    <xs:element name="name" type="xs:string" />
    <xs:element name="address" type="po:specialAddressType" />
   </xs:sequence>
  </xs:restriction>
 </xs:complexContent>
</xs:complexType>

</xs:schema>

public interface SpecialCustomer extends org.openuri.easypo.Customer
{
 public static final org.apache.xmlbeans.SchemaType type = (org.apache.xmlbeans.SchemaType)
 org.apache.xmlbeans.XmlBeans.typeSystemForClassLoader(SpecialCustomer.class.getClassLoader(), "schemaorg_apache_xmlbeans.system.s770F7AC969A9A1EBB5EE20A103CED4B6").resolveHandle("specialcustomera398type");
 
 /**
 * A factory class with static methods for creating instances
 * of this type.
 */
 
 public static final class Factory
  {
     ...
  }
}