Serious collection requirement violation of cisco.mso: undeclared dependency on cisco.nd (which isn't part of Ansible community package)

Do you mean the sanity tests run in CI? My guess is that the cisco.nd collection was installed before running the sanity tests. The sanity tests kind of assume that only the collections that the collection depends on (and transitive dependencies) are installed, so if you install other collections that are not dependencies, the import sanity test will not flag this.

I’m not sure whether Galaxy/AH actually run the import sanity tests: the galaxy importer which could run them does not install any collection dependencies (Galaxy importer: collection dependency handling), so the results of these tests would be mostly unusable (except for collections that have zero collection dependencies).