You may have this book but for the benefit of those who have not. This map is from. Kipinga. throwing blades of central Africa, Marc L Felix. I have drawn a thick line showing the modern Ethiopian border. The book concentrates on central Africa as in the title but to take that as written on tablets of stone would be a bit silly. I can see no reason why some sickle knife influence is not in these knives. Its easy being an arm chair general

but ideas are valid and it is best to thrash them out.