hi there,
on investigation of ND1 and ND2, there are pins that don't have external pull up resistors. Although these are not required, it is best design practice since the internal resistors that you switch on with;
GPIO_InitStruct.GPIO_PuPd = GPIO_PuPd_UP; or similar
are considered weak pull ups.
If the final board layout had all pins with external pull ups or pull downs, then you could use the pin right away. else, if these same pins were hard pulled to Vcc or GND this would effectively render these pins useless for anything down the road.
Ron