I dont know how to explain that more clearly. "Fast" is relative. Ok lets assume you are driving a car with 200 km/h. and i am driving a car with 200 km/h that is fast to a heavy loaded truck which is driving 30 km/h. But in comparison to me you are actually not moving. Means you are more than slow for me. I wonder that you cannot grasp that.
You are absoultely right, some ships are turning slower than others. Which does not mean they are slow turning. Ok to make it more clear. If one ship takes 10 seconds to turn and another one 9,5 seconds to turn than both are fast if you ask me. Where is the point. Actually saying they are fast is in the same way correct as saying they are slow.