Why does the iPhone talk to anything on the data port without entering the passcode first? It seems like this is reading the encrypted data and then brute forc

Why does the iPhone talk to anything on the data port without entering the passcode first? It seems like this is reading the encrypted data and then brute forcing it, but there's no need to give access to even the 'secure' data without asking the user to enter the passcode. Then you can check for 10 incorrect codes and wipe the device if necessary. (I believe this is how the Blackberry handles things)