The aim of the series is to cover a WMI Provider writing question  per post. If you have a question, you'd like the WMI team to answer, do leave a comment.

Now, for the answer -  

If the WMI client requests to enumerate all instances of a class supported by such a provider, a return code WBEM_NOT_CAPABLE will be returned.

 If the WMI client performs a query on a class supported by that provider and if that provider doesn’t have the query capability, then the query will fail because WMI uses the enumeration technique with post-filtering to provide the query results. However, if the query capability is supported by the provider, then the query will succeed because WMI will pass that query to the provider and the provider will handle it accordingly.

 Kapil Mathur [MSFT]