Is ManagerNetworkProtocol_v1.xml up to date?

There is a known issue with the service validator for this specific issue (see issue github.com/DMTF/Redfish-Service-Validator/issues/529).

The schema is correct; in CSDL, when extending an object's definition, the inheritance path points back to the last definition for the object with "BaseType". So, in this case specifically...
- In ManagerNetworkProtocol.v1_2_0, "NTP" the property is defined and points to the "NTPProtocol" inside ManagerNetworkProtocol.v1_2_0 as the object definition.
- In ManagerNetworkProtocol.v1_9_0, an extension to "NTPProtocol" is defined, and leverages the "NTPProtocol" definition in ManagerNetworkProtocol.v1_2_0 as the base definition.

The usage of CSDL in Redfish has an inheritance tree that we leverage everywhere, so version ManagerNetworkProtocol.v1_9_1 inherits from ManagerNetworkProtocol.v1_9_0, which inherits from ManagerNetworkProtocol.v1_8_0, etc. JSON Schema and OpenAPI need very explicit definitions, which is why when you look at a file like "ManagerNetworkProtocol.v1_9_1.yaml", you see the entire resource definition (and definitions of all nested objects).