Remember what these replays are. They are designed to be broadcast to thousands. The data would be highly optimised and compacted and you can literally see the effects of this. It's like lag, and on top of that they wouldn't be running the full physics model either. Make sure you aren't watching any form of network replay before judging physics.
I played the game today (and got a word with Kaz
) the car movement I saw looked great, very natural, especially the spins. The way the cars move the in streams is nothing like it.