I doubt you even know 10 bantu tribes, you're not in a position to declare who's descendants of slaves and who's not. I didn't say cushites didn't precede bantus in modern day south Somalia . But reer samaale surely didn't precede bantus in modern day south SomaliaAll Bantus in Somalia are descended from Slaves, this is a fact.
If you had any basic knowledge on the historical origins of Somalis, you’d know Somalis & their Ancient Cushite ancestors have been living in Eastern Africa long before the arrival of Bantus. The presence of minor Natufian dna even in contemporary Bantu ethnic groups in Kenya & Tanzania is testament to that.