The official display has a 5 pin header marked "GPIO".
One pin is marked "5V" and appears to be a power output. However, it is not connected directly to the 5V rail of the board which is available on the "PWR OUT" USB connector. Instead it is connected to the collector pin of Q2. What is the intended purpose of this pin, and why is it not connected directly to the 5V rail? What is the function of Q2, and where does this 5V supply actually come from? The voltage on this pin appears to be a few mV higher than that of the PWR OUT connector. Why?
Two of the pins are marked SDA and SCL, and they are connected to the same I2C bus that is available on the DSI connector. Why are they duplicated?
Finally there is the INT pin. This is not available on the DSI connector. What does it do?
Edit: Also, why is the unit supplied with a four pin dupont cable?