Hi Azipod
Welcome to the forum
As Fred said, with any vessel, if you decrease the throttle, the responce will decrease with it, since the propellor(s)/pods are not giving any thrust to turn you on the angle that your Pod/Rudder is facing.
Its like on an outboard engine, e.g. on our little fishing boat, if you throttle off, it is very hard to steer since there is nothing for the water to "Grab", since there is no thrust.
But oddly enough, this sometimes does fluctuate with different vessels, for example. our Colvic Watson cruiser will pretty much turn on her own length (She was built in the 80's-Sabb Inboard diseal), and even with throttle off, she responds very well (Because she has a rudder to turn her, unlike an outboard-that also add's to the steering), but of course, eventually, when you start to drift on the tide, you won't really get any sort of responce. (I'm talking about real life there
-Pretty much the same in the Simulator
)
Hope that helps on that one!
Jack