Ken sat near Jeff, Sanjay, and co while they were designing Spanner, and he regularly consults in an informal capacity on people's projects. I wasn't there, but it wouldn't surprise me at all if Ken's unique insight contributed to Spanner's design.
Ken's mind just works in a different way to most people. You explain your problem to him and he'll respond with some question or statement that turns your entire perspective inside out.
"The aggressive use of a small number of abstractions is, I think, the direct result of a very small number of people who interact closely during the implementation."
