I think you are being overly undercautious! There is a high likelihood that you will be stopped if you don't have your yellow fever cert. It doesn't matter what a website says. What matters is what local staff decide the rules are on the day you arrive. But you should still be able to enter the country after you pay a hefty fee and get the shot at the airport clinic, possibly hours after your arrival. Not to mention what happens if your flight is diverted or cancelled at NBO, etc. You are taking a huge risk flying through Africa without a YF cert.