I thing that the ports for the PIC18F and the PIC24_dsPIC should have added the following:
#define portPOINTERSIZETYPE uint16_t
The data pointers of this two platforms are only 16 bits (not uint32_t as defined by default in FreeRTOS.h).
Hi - you are indeed correct - if (when in the case of the PIC24) those ports get updated the constant will be added. The current port layer pre-dates the constant being introduced - and the definition in FreeRTOS.h is only a catch-all to allow older ports to build.
The definition used in FreeRTOS.h will not cause you a problem, but will most probably result in a warning being output by the compiler.