I guess that everybody is agreeing, although I have never heard anybody use the term "desired track" in aviation conversations before.
In zero wind, you point the aircraft at its destination and the heading you steer is the same as the track across the ground.
Once you introduce a wind across the ground track, you will need to vary the heading you steer in order to avoid being blown off your ground track. Part of your thrust is thus deployed countering the effect of the wind, and the speed at which you progress towards your destination is reduced.
No more to it than that.
2D
PS: Lets not worry too much about great circles
