And the reason for that is because creating such a duality makes it seem that both approaches are equally valid. I'm sure there are many more examples
Not true.
If you're going downhill, on any modern car the best is to shift into a high gear (4-6th, depending o the speed you're going downhill), such that you engine is running barely above idle RPM.
Then, the ECU will shut off the fuel supply altogether, and basically go into engine braking mode instead of keeping the engine in rotation by supplying it with a trickle of fuel. The braking effect in 6th gear is however minimal and thus even a very small slope is enough to keep the car going at a constant speed.
Eureka! -- Archimedes