At first I thought that geekmaster has faulty memory, but after inspecting the IRC logs it seems more like my memory is faulty. I could swear that we did already discuss this ... well maybe not.
Yes the trick with mmcblk0p4 is that it doesn't contain the FAT filesystem directly but instead for some reason I still don't understand it contains a partition table and then the FAT filesystem.
As for the output (created by fdisk) ... the nonexisting device names like /dev/mmcblk0p4p1 are not a problem. It is just fdisk trying to be smart and helpful by telling user what the device names for the partitions most likely are (it is in no way attempting to access them).
So now I told you. Better late than never, huh?
I would really like to know what made people at Amazon decide to do this.