I think what Roman means is that big African cities are more likely to be regarded as the low points of overlanding trips - or just opportunities to take care of practicalities.
No idea if anyone has or hasn't done the trip you describe, but I doubt there's a trophy going for first place. The time for record-breaking attempts has probably gone.
You might need more motivation than a publicity strapline to want to visit some African capitals. At any one time there is usually at least a couple that are a bit 'tricky'. Mogadishu springs to mind, without thinking too hard!
Still, any excuse to go...