You need to support it if you want to properly support removable SD cards. Microsoft managed to make their patent encumbered exFAT file system a required part

You need to support it if you want to properly support removable SD cards. Microsoft managed to make their patent encumbered exFAT file system a required part of the SDXC card spec, just as their much-abused patents on FAT32 were expiring. I guess it is gracious of them to partially undo the damage they've done, now that they have given up on Windows Phone.