Looks good!
Good times!
There won't be as much heat rejected with the control lever on HOT and the fan off, but there is still air going through the core (it's not stagnant). The fan being off doesn't mean zero airflow. It's a lot easier to reject heat through a radiator than it is a rubber hose.
Also, I think there's a lot more resistance to flow when the coolant has to snake through the heater core as well as past the control valve, than just a short hose loop. It's definitely not negligible.
In the bigger picture, whether you have a heater or a loop, the engine will be OK in normal street driving. I haven't run through the calculations, but I'd like to think that the engineers sized things correctly, or as best as they could. It's when engine demands are increased that a loop from the head to the WP inlet will have a detrimental effect (dangerously unstable temps at back of head).