Not true.
KDF was Kamba+Kalenjin affair in colonial period. This was because Mzungu ruled they had best military aptitude.
"In 1959, the Kalenjin, Kamba, Samburu, and Northern Frontier pastoral communities supplied approximately 77 percent of the total strength of the Kenyan KAR battalions.'"
Jomo came - and when he found it hard to crack - he created paramilitary GSU and trained APS - with his tribesmen- so they could provide a counter in case of a coup or mutiny.
Tonje fixed appointment - except top generals - where president has a say.
The military has been tribalised since the days of Arap Moi. Before that the military was a Kamba affair and Moi changed all that to bring in his people. Now after 20 years Kikuyu domination it has turned to be a Mt Kenya affair. Am even surprised Uhuru has a few other ethnic groups at the top of the military.