You need to stop writing massive essay replies and keep it to the point man.
There is no evidence of Arabian males from the medieval era fathering millions of Somalis. It is so unscientific and ridiculous I won't even bother providing more arguments.
My family has 100 people just between 1920 till now, that's one family and my grandfather had about 4 wives. Plus each man marrying 4 wives and un-marrying could lead to thousands just a century x by 1000 years you could have millions niyahow of people. It's mathematically plausible. U don't account for the fact it's haram to make up fake fathers, maybe your not religious conscious but study the ayah about zayd bin harith and what happened when the prophet tried to change his name to his own, he was blasted for it and told noone can create fake fathers.