I realize this is an old post, but the only relevant thing I see. I'm having the same problem (now with current versions of everything).
I tried removing the NavigationViews as you mentioned but that didn't help.
In fact, the NavigationView that is in the SceneBuilder (you are right that I hadn't noticed that one) isn't part of the Preview process. The preview starts with the "PreviewProvider" in the top-level ContentView so the NavigationView in the SceneBuilder has no effect on that.
I tried adding NavigationView around the call to ContentView in the PreviewProvider, and that actually made my clicks really do navigation in the preview, but I still don't get the NavigationTitle in the preview! I tried hiding the NavTitle in the PreviewProvider code and that made no difference.
If anyone has any further ideas on the OPs original topic (which is also my topic) I'd very much appreciate your feedback.