As per the documentation: https://docs.redhat.com/en/documentation/openshift_container_platform/4.19/html/support/gathering-cluster-data#gathering-data-specific-features_gathering-cluster-data

The version of the rhwa specific must-gather is linked to the latest NHC version released. The last delivery RHWA 25.8 is not including a new must-gather image (v0.10.0), being a mismatch between the documentation and the actual availability of the images.