PCA plots can be misleading sometimes .Kikuyus got nilotic admixture besides their cushitic admixture unlike Somali Bantus who are a more direct cushitic-bantu admixed people as far as I know. If you check their position, Somali Bantus are literally inbetween ethnic Somalis and West africans. Kikuyus must plot with them here because this PCA doesn't differentiate well the West African, the Nilotic like found amongst cushitics and the proper Nilotic ancestry. Where would a mixed half Yoruba half Somali plots? Where those Somali Bantus are located. The PCA I posted is from another study using the same Somali samples, you can see more clearly how these three Jarreerweyne(in green) are inbetween ethnic Somali and "pure" Bantu/ West africans. They're close to Kikuyus, some rwandans but not exactly overlapping with them since they don't have this slight proper nilotic admixture which make them(Kikuyus, Rwandans) closer to Nilotics on the top left corner. Their admixture is seen on the second screenshot amongst the "Somalia_Somali" group, They don't seem to be only 30% Somali-like to me