2.5.1.6. Section 6: Other System Attributes. Optional for an IS-CDD with the exception of consideration should be given to identify the system categorization for information systems and PIT systems as a required capability - the potential impact (low, moderate, or high) resulting from loss of confidentiality, integrity, and availability, if a security breach occurs IAW Reference [10].

For reference or comparison, below is what the JCIDS Manual says for the CDD 2021 itself:

2.5.6.2.1. Future integration platforms. Used in cases where integration on certain platforms is not currently planned or resourced, not already captured in the IOC and FOC definitions in the Program Summary Section of the ICD (Section 4), but the Sponsor would like to preserve the option for future integration on additional platforms.