[GR-63227] Update SBOM BuildOutput.md, describe unassociated types

PullRequest: graal/20386

Author: rudsberg

docs/reference-manual/native-image/BuildOutput.md

@@ -269,6 +269,10 @@ When embedded, the SBOM size is displayed.
 The number of components is always displayed. 
 The SBOM feature can be disabled with `--enable-sbom=false`.
 
+Unassociated types are displayed when certain types (such as classes, interfaces, or annotations) cannot be linked to an SBOM component.
+If these types contain vulnerabilities, SBOM scanning will not detect them.
+To fix this, ensure that proper GAV coordinates (Group ID, Artifact ID, and Version) are defined in the project POM's properties or in _MANIFEST.MF_ using standard formats.
+
 For more information, see [Software Bill of Materials](../../security/native-image.md).
 
 #### <a name="glossary-backwards-edge-cfi"></a>Backwards-Edge Control-Flow Integrity (CFI)