why my extract variable policy not failing even with IgnoreUnresolvedVariables "false"?

[#1]

Below is my policy example, please let me why no fault has been raised if referenced xpath is invalid.

<ExtractVariables name="Extract-Variable-Submit-Request">
  <IgnoreUnresolvedVariables>false</IgnoreUnresolvedVariables>
  <URIPath>
    <PatternignoreCase="true">/sendEmail/{BusinessProcessId}</Pattern>
  </URIPath>
  <XMLPayload stopPayloadProcessing="false">
    <Namespaces/>
    <Variablename="Item" type="nodeset">
    <XPath>/Data/Item</XPath>
    </Variable>
  </XMLPayload>
  <Source clearPayload="true">request</Source>
</ExtractVariables>