Hey dknutsen thank you for the guidance!
It should have been obvious to simply return a Ember.RSVP.hash() from the report route model hook. Derp on my part, good catch! As for the overall decision to set the selected report on the parents controller I’ve a specific reason for doing so but I get the feeling it’s because I’m simply lacking in experience with Ember’s routing system. The action inside my routes controller that sets the selected report is what allows my dropdown of reports to show the right selection. My problem arises when I use the back button (or forwards) or I refresh the page directly to the nested route. The dropdown never gets set. Ultimately what I figured would be the right thing to do is somehow pull out the dynamic segment from the route such that the reports route can set up its controller each time and the child route could then not worry about it. Btw you were correct about my dropdown getting set twice 
I happened to find another person who has the exact same problem as me. No reply to his question though.