The fan draws air into the vent. The temp sensor is in there somewhere. But really, is that the only place to locate this thing?
The glass dot is a light sensor. During the day, the display is bright. If you cover the sensor simulating night, the display should automatically dim.
The crappy cupholders is intentional.... My old 03 VW Wagon was worse. It was made of a bunch of plastic sticks that fold up into the dash when stowed, located above the radio. Even a small bump would jiggle you coffee so it spilled all over the radio, gear shifter and you and your passenger's pants. Newer VWs had a much better design.
I'm convinced that the German cupholder engineer had a mad scientist moment....
"Hans.... look where I put zee cupholder! Ist right nix to zee HVAC sensor! Ha ha ha ha ha ha. Now zee American will be kalt when he tried to drive with a hot cafe!! ha ha ha"