While line 640 mentiones security, privacy, and reliability the section speaks of security at the communication layer only. ISO's need comply with NERC CIP Information Protection guidelines that should be described in the Information Model (see IRC Information Model and XML Schemas) to classify information, not only protect it.
The information structure correctly describes the information classification for NERC CIP, but including the "value" of the message in the message seems to increase risk by flagging more valuable messages. (From discussion with CSWG members)
This would be a useful "deployment descriptor", rather than a message component.
This seems to be relevant information in deciding what security/reliability to compose for specific types of interactions.