I don't work at Facebook, but I'm fairly certain this is for things like build servers, not client machines.
They use Munki for software updates, which, just like you describe, gives the user a grace period where they can reboot at their leisure. Ignore it for long enough and it'll crank up the nagging, and eventually force a reboot.
They use Munki for software updates, which, just like you describe, gives the user a grace period where they can reboot at their leisure. Ignore it for long enough and it'll crank up the nagging, and eventually force a reboot.