For a moment take a step back from having a straight look at the components, and take a look at the game loop. It has a structure oriented on tasks: Processing input, a first animation pass, physics, collision resolution, perhaps a second animation pass, and rendering at last (more or less; details are not important here). Notice that the tasks are based on top level sub-systems, and depend on components managed by probably lower level sub-systems.
Looking at the rendering sub-system, does it need to be notified about position changes done in any of the animation, physics, or collision tasks? No! At the moment of rendering, the sub-system can safely assume that any and all positions and orientations (i.e. the entire placement) are settled and well defined, because beforehand running sub-systems have done their jobs. Any notification of a "RenderComponent" (I use it here for clarification; I'm not a fan of RenderComponent at all) done before would be a waste.
Looking at the collision sub-system, does it need to be notified about position changes? No! Because collision detection is a self-contained process, running in its entirety but not on request on every little move.
Of course, having an explicit motion sub-system (or using the animation sub-system) requires a way that the sub-system can set the placement as needed. There need to be a reference from the animation sub-system to a placement component (which is probably managed in another sub-system). But there is neither a need for an animation component (whatever it means exactly) to refer to the placement, nor for the placement component to notify the animation (component or sub-system).
In summary I mean that in consideration of all the discussion of linking, messaging, slots and whatnot, one should in the first place think whether notification in each particular case is needed at all. The use of sub-systems allows for concentrated and perhaps in order processing, and that does not work well if the program jumps forth and back in code. Concentration may be yielded in by letting one and the same sub-system handle different but related components, too. (All this does not exclude that in some cases notification may be meaningful.)