Hey guys – we’re aware of these issues, and plan to give this feature some attention in 2017.
Our plan is to ensure that streaming content works in both the ways you’ve described: Radio should optionally include content from TIDAL when you want to discover new music, and Radio be able to start on any content, whether it’s part of your library or not.
This work will not be part of our upcoming 1.3 release, but it is coming, and some pieces of infrastructure are in place to help us gather data to improve the selections made by the Radio algorithm, and to cut down on repetitive selections.
Look for Radio to get a lot better, guys. Thanks for the feedback!