incorrect flagging of violation of cos-all-limited

<?xml version="1.0" encoding="UTF-8"?>
<xs:schema
    xmlns:xs="http://www.w3.org/2001/XMLSchema"
    elementFormDefault="unqualified">
  <xs:complexType name="base_open_content">
    <xs:openContent>
      <xs:any notNamespace='##local' processContents='lax'/>
    </xs:openContent>
    <xs:all/>
  </xs:complexType>
  
  <xs:element name="root">
    <xs:complexType>
      <xs:complexContent>
        <xs:extension base="base_open_content">
          <xs:all>
            <xs:element name='child' type='xs:string'/>
          </xs:all>
        </xs:extension>
      </xs:complexContent>
    </xs:complexType>
  </xs:element>
</xs:schema>