Earlier quoted context omitted.
It is a scalding hazard though. At 70°C skin burns occur in about a second or so. The thermostatic valve makes it so that the water that comes out of the water heater is at a more reasonable temperature.
It's supposed to be HOT water, not lukewarm... I have my water heater set to 150F because it makes the hot water last longer, especially in the winter when the incoming supply is barely above freezing, but that doesn't make the tank bigger.
If the automatic mixing feature malfunctions to super-hot, then it could be risky...