Mike notes that the example of redirect_user with a custom URI with a query parameter was helpful, and suggests extending the normative language describing it in Grant Sec 3.3.6 would be good. E.g.: "Providing a value in this response might be appropriate, for example, if the URI needs to be customized per requesting party with a query parameter."
Per UMA telecon 2017-06-29:
Mike notes that the example of redirect_user with a custom URI with a query parameter was helpful, and suggests extending the normative language describing it in Grant Sec 3.3.6 would be good. E.g.: "Providing a value in this response might be appropriate, for example, if the URI needs to be customized per requesting party with a query parameter."