ALL Forecast Category Picklists unavailable for user.

When logged in as user that has access to edit the standard Forecast Category field, users should be able to see ALL the active Forecast Categories and be able to select one and save, regardless of what Stage the Opportunity is in. Salesforce state that this is possible when using Lightning Experience. Has anybody seen this before? Know of a setting that might be wrong etc as this is happening across all sandboxes and Production. Thanks in advance.