If the WHOLE package (as you described) was called graphics, a finished still image wouldn't be called graphics...or complete. Yet, a still image IS complete and called graphics. That breaks your logic of "the whole package we call graphics".
Context. Humans have this incredible ability fit the same word to different situations, with neither use being technically incorrect.
My chum who works in offline rendering for tv would never use the words "graphics" to describe a single rendered frame, unless it was understood that frame was representative of a sequence of images or of a particular graphic design being used for a sequence.
Are you saying that particle effects, etc disappear in a still image? If not, I don't see how your point holds up.
There are some effects that require multiple frames to show themselves. How do you explain temporal AA and accumulation buffers, if they aren't part of rendering?