The essence of K2-DirectConElemNamespace-17 is that 
<e xmlns="content{{"/> is invalid.

However the XQueryX version of this test is:
<?xml version="1.0"?>
<xqx:module xmlns:xqx="http://www.w3.org/2005/XQueryX"
            xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
            xsi:schemaLocation="http://www.w3.org/2005/XQueryX
                                http://www.w3.org/2005/XQueryX/xqueryx.xsd">
  <xqx:mainModule>
    <xqx:queryBody>
      <xqx:elementConstructor>
        <xqx:tagName>e</xqx:tagName>
        <xqx:attributeList>
          <xqx:namespaceDeclaration>
            <xqx:uri>content{</xqx:uri>
          </xqx:namespaceDeclaration>
        </xqx:attributeList>
      </xqx:elementConstructor>
    </xqx:queryBody>
  </xqx:mainModule>
</xqx:module>

As far as I can tell this should be valid, and equivalent to
<e xmlns="content&#x7b;" />
and as such is not an appropriate test.

The XQueryX version of K2-DirectConElemNamespace-18 suffers a similar flaw.