[Endoperez]

There are two kinds of stealthy commanders: scouts and spies. Everyone who isn't a spy can scout: Pangaean harpies, normal Scouts, nation-spesific Scouts, a Van or -Centaur commander that you'd normally use to lead an army, even a stealthy mage like Pan. They are all equal when it comes to describing the land they are in.
Then there are spies. Ulm has them, and Marignon, and few other nations. Machaka has Eyes of the Lord, Man has Bards, etc. Spies are stealthy commanders that can 1) cause unrest via a special command and 2) give you much more info about the land they are hiding in. There's no in-game special tag for spies, so sometimes it can be hard to tell whether or not a unit is a spy.