I think Ogabe handled that problem when he went over to 'campaign' for his cuz Raila Odinleberry. But we can always hope it still exists.
They were johnny on the spot with their inaugural stamps;)
I believe that they wanted to cut loose from the colonial constitution that was bequeathed to them in 1963, KNEW they were after a Republic, and could easily have started using the term in the meantime. We need a Kenyan with experince in the promulgation of public records in the time period in question to resolve the issue. It's a question, for sure, but in the end it may be of no importance. The key issue is what's on page 5733 of Book 44B. Can someone please check?
https://www.cia.gov/library/publications/the-world-factbook/geos/ke.html
What you know and what is fact are two different things. Go to the address above and click the first green INTRODUCTION +.