I was able to reproduce this situation and the message can indeed be confusing so I logged an issue internally so that the error content can be improved; thanks for reporting this situation.
Having said that, despite the confusing error the behavior of not enabling a third-party client explicitly is to be expected. The reasoning here is that once you promote a connection to be a domain connection the it will be available to all third-party clients so there’s no need to explicitly enable them individually at the connection level.