In truth, the "job security" thing is often as much a matter of personality as it is explicit strategy. The "XYZ guy" often becomes that person simply by being someone who is stubborn enough to tackle integration problems most people would rather avoid, and by being willing to deeply embrace "RTFM".
To say they've established "job security" can sometimes seem like a cynical read on their roles, but I think it's always good for teams to have a few devs with this sort of personality.
