In OData, the value 'none' appears both when the RAG status is not enabled for a Review and when it is not completed in a Review that has this field enabled.
To identify Reviews where the RAG status was set, filter for Reviews with a completed status. If a Review is completed and has a set RAG value, it indicated that the RAG step was enabled during the Review. If it shows 'none' then the Review was not configured with the RAG step.