I don't recall where I saw the demo but I think I know what he is talking about -- or at least can provide related information.
The problem with the character not moving on the screen, being fixed at the center, is that the human player will not perceive any motion. The user will immediately feel that something is wrong, but perhaps not be able to pinpoint it. If the character is moving it is essential that some kind of actual motion is done.
One of the concepts used here is the player box. This is a region of the screen where the character always resides. Unlike a fixed location however the character can actually move all around in this box. The screen only starts to scroll as they approach the edge of the box. This means that each time the user changes directions they'll actually see their sprite move on the screen (regardless of what the background is doing).
From here you can start improving the effect by experimenting. Some games slowly center the character in the box again. Some have a kind of logrithmic box so that the first movements move the sprite a lot, but less and less as they get to the side of the box -- or this may be tied to the character's speed as well. What works well depends on your game, and by no means is there a definitive "best" solution.