You want either motion smoothing (of the 60->120fps kind) or black frame insertion on an OLED for good motion, otherwise the lack of decay between frames will make it look unnaturally juddery.
I don't think that is the case when watching a movie. What does "unnaturally juddery" actually mean in that context? For a modern movie (after 2010), if they wanted a different look they would have filmed it in a higher "capture rate".
A movie projector will have fading or black frame insertion between each frame. An OLED displays the picture completely still and then instantly changes to the next one. If you're looking closely, that will seem unnatural.
Playing something like The Dark Knight Rises from an UHD Blu-ray on a good OLED looks incredible!