"Put the saucepan on the stove."
Translation:Поставь кастрюлю на плиту.
It's may be normal and natural for some native speakers, but "поставь кастрюлю" is more correct.
Why is "на плиту" (Accusative case) used here? Shouldn't the focus be on the final position (-> prepositional "на плите") instead of the movement towards this position?
I think that the accusative case is correct. Extending your suggested reasoning, the prepositional case would be used only if there were no movement. If I translated, e.g., "Yesterday I walked to school," I would use the accusative "в школу" even though I were в школе after the action ended.