On the b777 and the b787 when only using reverse thrust on the right engine, you can see that the reverser doors are open but the engine still pulls the plane forward.
On the CRJ-900 only using reverse thrust on the left engine results in reverse thrust output in both engines even though the reverser doors on the right engine are not open. On the other hand using full reverse thrust on the right engine only results in idle reverse for that engine.
