"Its less about how clients exchange data.
[...]
In the "syncronous simulation", each client is calcualting
the world logic, only based on usercommands from
all clients.
The server (such as battle net) would just handle
the connections and transfer of the commands.
"

That's what I'm saying and I'll show you how:

As you say, P2P is more than just the network; it's also what the apps do with this net traffic.

Consider a 3-tier architecture: presentation, logic, and database. In a C/s environment, the client is solely responsible for presentation, that is presenting the information to the user. The server is solely responsible for the logic and the database, that is a the rules and the charge that dominate the game. In a P2P environment, every peer must have some or all of these components present. Presentation is obvious since every peer is connected to every user, logic is necessary since every peer needs to know how to calculate its own game state and perhaps those of others, and database is important sense each peer it needs to know its own statistics for the world.

So we are both saying the same thing, that even though this is a C/S platform and the packets don't flow like in a P2P, it is in fact being enacted as a P2P architecture in that each client has complete autonomy from the server and the server, as I and you stated, is merely relegated to the role of a fancy router.

As for SC2, I wouldn't assume. I don't know any better but 9 yrs is an eternity in networking. I would imagine Blizzard has been constantly updating their net model in other releases and thus it could bear little similarity to SC. Having said that, if it ain't broke, don't fix it... if it worked in 2001 and works today, then it is truly worthy of attention.