Fans on Turing Pi 2

I'm aware that there are 4x headers for fans, one for each board (Pi CM4, NVidia, Rk1 etc.). And the documentation also shows the 2-pin 12V fan header for a main cooling fan which is located between the RTC socket and the Node 4 UART 2 pins. Docs at https://docs.turingpi.com/docs/turing-pi2-specs-and-io-ports-case-and-cooling#cooling.

But on my board I also see holes to solder a 4 pin header labeled 'FAN' and J16 which is immediately next to the Node 4 UART2 pins; there is R437 on its other side.

Does anyone know what this is for? I was rather hoping this was for connecting a 5V (or 12V?) PWM fan; there must be a temperature sensor on the board as the 4x headers for the fans for each of the 4x boards are 4-pin PWM.

I have bought and am planning to mount a separate fan and thermostatic controller but if it's built-in it'd be much easier to use that! Anyone?