I don't think that this is brute-forcing the passcode at all, rather I think it is brute-forcing another method to locking the iPhone, namely that of iTunes...

I don't think that this is brute-forcing the passcode at all, rather I think it is brute-forcing another method to locking the iPhone, namely that of iTunes... iTunes has a special file on your computer that when you plug in your phone will allow it to start syncing data to and from your phone (including making backups) without requiring you to unlock it. What I believe they are doing is actually brute-forcing the required entry code for that. Once you get that code (and there is no limit to how many times you can try) you get full access to the phone, including that bit-for-bit copy they are talking about. Apparently the key space is small enough that it is easy enough to brute-force. In that case it doesn't matter what kind of protection you use, whether it is the pass code lock, or the alphanumeric that they introduced on the iPhone 4 (IIRC). Note that all of this is speculation, I have no inside knowledge, but that is how I would go about attacking the iPhone.