This does imply that Tim fans wouldn't even be able to conceive Tim as a character past any actors skin color
I'd like to think the costume and being a geeky loser techkid Robin would reflect the character but its not the same for every fan
I don't like Duke being the go to substitute every time the question of raceswapping a Robin comes up. Duke doesn't bring the same dynamic to Batman(or the other Robins/Titans) that any of the other robins do. The story would change by including him mind you.