I probably ended up on SO hundreds of times in that period, and never once saw Documentation mentioned (I _may_ have technically seen it in the nav bar, but just seeing "Documentation" in that context I'm going to assume it is documentation _for_ SO and just ignore it).
E: Forgot to mention, even reading the title of this post my initial thought was that it was documentation relating to the sunsetting of SO (which sounded crazy).
And I thought it was Stack Overflow sunsetting the very idea of tech documentation because now everybody just read the SO thread for everything they want to do, which is even craziest.
Few announcements through regular comment notifications would be fine to me even if not interested.
Look again. There is DocumentationBETA in the top bar, it has been there since they started the project.
Anyway, who looks at the navbar? People get there by googling a problem they are having now. They're in hurry, no time to look around.