You are disposable though, everyone is. It's generally a losing game to try to cement your position by playing gatekeeper on institutional knowledge, because at best it will prevent you from ever being promoted, and at worst will peg you as a single-point-of-failure liability that needs to be dealt with proactively. I understand this sort of defensive posture might make sense in some companies/situations, but the article is clearly talking about software engineers in large upwardly mobile companies. In those situations it's essential to have a non-adversarial and trusting relationship with your boss, if you don't trust your boss than that's the first thing to address by any means necessary.