I'm not so sure about that. It depends on the country, and I can't tell for Kenya.

As far as I can tell, most if not all country apply the same 6 month to expiration policy to deliver VISA from the outside, but I have never heard of someone at a border being denied the entrance for that reason.

I mean, the passport IS valid, and you are at the border.

I assume in many places of the word, they'd let you pass, or you could bribe them to let you pass. I'm by no way saying it would have been a smart move.

What I'm saying that a valid passport not being valid doesn't make sense.

While it is indeed the duty of the traveler to get informed, you can't really expect people to think about it if they're not experienced travelers.