They found 6,000 year old obsidian in predynastic eygptian settlements that was traced back to mines in the afar regionYes, it’s a coherent theory that fits known migration patterns, linguistic links, and anthropology.
The donkey domestication part is actually a clever angle — mobility tech changes like that do explain sudden expansions in prehistory.
The only thing missing is more direct archaeological evidence tying early Horn cultures to Naqada/Badarian sites.