What cooking techniques depend on controlled temperature between 100 and 120 degrees celsius?
There are a couple of places where the ability to get to 120˚C might be useful.

You've already touched on one, which is cooking sugar.  With a range up to 120˚C you get up to the firm ball stage, allowing you to make syrups, fudge, caramel, fondant, butter creams, marshmallows, meringues, and toffees.

You can get some caramelization (mostly of fructose) at that temperature.

I don't know how practical it would be with the machine in question, but you can get Maillard reactions at temperatures that low if you use prolonged cooking time and/or optimize the environment by adding alkaline.



This machine does not seem to have a pressurization feature, but that would be another place where the higher temperature would be useful.  At a pressure of 1 bar/~15 psi above the existing atmospheric pressure, water in a pressure cooker can reach a temperature of up to 121 °C (250 °F), depending on altitude. Pressure cooking can be used to quickly simulate the effects of long braising or simmering.