Responders don't use valid? to check for errors in models to figure out if the request was successful or not, and relies on your controllers to call save or create to trigger the validations.

My only concern with this approach is that if someone calls #valid? on the form object afterwards, it would under the hood currently delete the existing errors on the form object and revalidate. The could have unexpected side effects where the errors added by the models passed in or the service called will be lost.

My concern with this approach is still that it's somewhat brittle with the current implementation of valid? because whilst valid? appears to be a predicate and should have no side effects, this is not the case and could remove the errors applied by one of the steps above.