Extraordinary (double) Exchange Sac - Karjakin vs Radjabov

For a short period of time I (had to) play the very aggressive but always unpleasant sharp variations of the Sicilian Dragon. Actually, I once managed a nice victory with a (not 100% correct) but typical Knight-sac on f3 and exchange-sac on c3:

However, this post is not a very late kind of posing on any of my games - I am not that type of guy (and actually this is the first time I publish a victory of mine). It is about a very intersting "Bf6"-move by Black initiating an impressive double exchange sac that made me not only recall my own game but thinking about putting both online and share:

 

Bf6 - escaping the exchange of the dark-squared bishops and sacrificing the exchange: excellent thinking!

Kasparov versus Karpov

In the following game, Kasparov fights Kasparov and went on with Rd3.                                            My initial thoughts: Why would white want to do this? According to my understanding, bishop and knight are “somewhat preferable” over 2 knights. Yes, I know that this position anyway favours bishop over knight and I see that the white knight is currently lacking a good square and once the white knight re-positions, it might get swapped-off the board anyway. So yes, the exchange in general favours white and might be inevitable.  But why now?  Black´s queen and rook are (mis-)placed behind the rook on c5 – so why free the line for them?

Regardless of all the above, I would judge the position being absolutely equal, so does the machine. Just for the sake of it, I played h4 - still things are absolutely equal (+0.15 for white).

So why does Nd3 receive an exclamation mark?