Not sure of the intent of this shall not-it seems that what the recipient "shall" do is decribed in the bullets above and below this bullet-if it could be combined with what "shall" be done to address the error-that may help although that may be what the other bullets address...

Existing Wording:

In situations where information on a particular data element is not present and the reason for absence is unknown, the Sender SHALL NOT include the data elements in the resource instance as part of a $process-message operation or a query response