Another factor: this is a board intended for a RPi. Its GPIOs are 3.3V, but the PMOS switches VCC_INT which is 5V here if I'm not mistaken.
Meaning that if the gate was directly connected to a GPIO, it may not be able to switch off the PMOS properly. There is a pull up to VCC_INT, but it will do nothing when the RPi is actively controlling the GPIO. It will keep the PMOS switched off when the GPIO is in high impedance though.
The fact that you'd find 5V on the GPIO through a 47k resistor would be harmless per se for the GPIO itself when it's in high impedance.
I don't know enough about the RPi GPIOs, and the library/language used here, to know if you can properly put them in high impedance programmatically. If so, a program could just set the GPIO to output/low level to switch the PMOS on, and set it to high impedance to switch the PMOS off, instead of setting it to a high level (which again would probably not work well.)