BRD_SD_MISSION (storing missions on SD card) not available on CubeBlack / F4-boards?

Hi everyone,
since ArduCopter version 4.3.6, there allegedly should be an option ‘BRD_SD_MISSION’, which allows storing missions on the SD card instead of the internal FRAM.
However, this option is not available on two of mine CubeBlack FCs flashed with ArduCopter v4.5.4.
Does one need to enable this explicitly, or custom compile the firmware for this? If so, which flag / command needs to be set / passed?
Or is this feature generally not available on F4 boards? If so, out of curiosity: What is the limitation here?
Many thanks in advance.