There is some uncertainty related to what a server with a profile allowing exclusion of Name Space 0 must include when it derives types from a type defined in namespace 0.
In Part 5 v1.04 Clause 8.2.6 it states:
"The intention of the “ObjectTypes” Object is that all ObjectTypes of the Server are either directly or indirectly accessible browsing HierarchicalReferences starting from this Node. However, this is not required and Servers might not provide some of their ObjectTypes because they may be well-known in the industry, such as the ServerType defined in 6.3.1."

This seems to suggest there is no need to expose the standard types however the NanoEmbedded profile states:
“Exposing types in the AddressSpace is optional for this Profile except if custom types (i.e. types that are derived from well-known ObjectTypes, VariableTypes, ReferenceType or DataTypes) are used.”

Why is this predicated on not having custom types?

For example if a nano server has an instance of a PropertyType Variable a browse response would include the HasTypeDefinition Reference to PropertyType with the extended NodeId being namespace 0 and the well-defined Id of PropertyType however a subsequent browse or read using the PropertyType NodeId would fail since the server elected not to include NS0. This would seem to be acceptable by the definitions above.

If we then consider a similar example but with a derived Variable type such as:
For example if a nano server created a VariableType derived from BaseVariableType called MyVariableType when browsing from an instance of MyVariableType the response would include the HasTypeDefinition Reference to BaseVariableType with the extended NodeId being namespace 0 and the well-defined Id of BaseVaribleType however a subsequent browse or read using the BaseVariableType NodeId would fail. From the client’s perspective this would seem to be the same case as the previous example suggesting that there is no need to define a special case for derived types.