First of all, the injectors on direct-injection (GDI) engines will get cleaned the same way as manifold-injected engines when the gasoline detergents pass through them. There could be a need for really good detergents since the injectors would be subject to the harsh environment of the combustion chamber, but that's the only difference for them. In terms of valve, the exhaust valves are no different in GDI vs. manifold injection engines.
The issue of most concern is that that since the fuel goes directly into the combustion chamber, downstream of the intake valves, the detergents won't ever contact the tops or "backsides" of the intake valves to clean them. The reality is that much of the "carbon buildup" on intake valves actually comes from the fuel itself. In manifold-injection engines, the air/fuel mixture passes across the top of the valves, and some of the chemicals in the fuel can bind to the backside surface of the valve. Since GDI engines have fuel bypassing the valves, it never touches the backside and thus there should be no buildup from the fuel itself.
The only buildup the intake valves would be exposed to is oil residue from the PCV (crankcase ventilation system). Air from the valve covers is sucked into the intake manifold in order to vent the lubricated areas of the engine. If the car's PCV system is not very good at keeping oily residue out of the manifold, it can be an issue with valve deposits. Since detergent gasoline never passes over the backside of the valves in GDI engines, it would not get the benefit of that cleaning.
Dumping all the Techron or other fuel cleaners into the tank won't help clean GDI intake valves. If I were particularly worried about it, I would use a product that that is sprayed into the intake manifold. That's what dealers charge over $100 for. While the can of spray is about $15, there is labor involved. The spray must NOT be drawn in through the MAF (mass airflow) sensor because it will damage it. They have to either remove the MAF sensor or use a vacuum port on the manifold, downstream of the MAF sensor. They will likely spend an hour of labor, so that is the majority of the cost. If you can DIY, you can save a lot of money buying a $125 can of CRC brand cleaner fro GDI engines.