The problem is that you are thinking of it as a general-purpose computer rather than an appliance.
Look at it this way- I go to Best Buy and purchase a particular model of wireless router; it is version 'n' of the hardware and runs a Linux core. The next week, I go to Staples and purchase another of the exact same brand and model of router, only to receive version 'n+1' which now runs VxWorks. Both meet the same functional specifications as outlined on the package and both have the same configuration GUI. Nowhere was I guaranteed that I would get a Linux-based router.
Its the same here. Each Africa may have different internal hardware, but that is all hidden by running different ports of the same OS and applications and only guaranteeing the same minimal functional level. The issue comes when a power user decides to move beyond the installed functionality by adding a software package which is not available for the archtecture of his specific Africa (ever try to find modern CE software for anything other than ARM?), but this is not the target audience of the device.