I disagree, any fuel will produce carbon deposits when it is burned. That's how combustion works, period. However, 30k miles is pretty early for the carbon to have accumulated to a point where you would need to clean it out. Usually it is good practice to have this done around 50 or 60k.
Then again, you're under warranty, so who cares? Have them flush it out for free, it can't hurt to have a clean engine.