You need the increased space, which means you have the traffic waves.

You need the space because of variations in cars; some have better brakes than others, some may be heavier so need more time to slow down, others may be on wetter patch of road, etc.

And one car may not even get the signal, so only slows down when it observes the vehicle ahead of it doing, an observation that needs time.

Or a car starts accelerating as the one in front just stalls.

It may all be better than human reaction times, but for robustness, which is really very necessary, you're going to get the same dynamics.

And this all assumes only good actors; somewhat optimistic in my view.