Yes, focus accuracy. When lens designers design a lens with manual focus ability as well as autofocus, they need to choose one of two defects. In order to have fast autofocus, the total movement of the focusing element needs to be small. This makes accurate manual focus nearly impossible as there is a minimum amount you can move your fingers. In order to gave accurate manual focus, the total movement of the focusing element needs to be large. This makes autofocus very slow. When you are only moving an actuator and the motor moves the focusing element, it is possible to have large finger movements giving a small lens movement.
An example from my older lenses: my 1983 Cosina 50 mm lens needs you to turn the focus ring through 300 degrees to move from 1 metre to infinity - allows very fine adjustments. My old 18-55 kit lens needed you to turn the focus ring through about 30 degrees to change the focus the same amount - only allowing coarse adjustments.