For exemple, I have create an inherited process named TestNewProcess8 from CMMI and as u can see below the reference name of the WIT Review is by default "Microsoft.VSTS.WorkItemTypes.Review".
I tried to use this API, https://docs.microsoft.com/en-us/rest/api/azure/devops/processes/work-item-types/update?view=azure-d... to update the WIT but we got an error that says the reference name is not found in this process :
The only way to reference the WIT is to edit it with Azure Devops interface. Then the reference nam is automatically change and works with API as we can see below :
