Not much of a secret when Shiori knows, but I think it's in Kurama and Botan's nature to LET HER THINK that she's slick with catching certain hints they leave. Shiori likes to be involved and by golly they'll involve her as reasonably as possible. Let her feel smart! 

Gotta get all the light out the way to make room for impending darkness, yeah? I think that's been our style for a long time now anyway.