Freewheels and freehubs are two entirely different animals. All Shimano freewheels I've come across have needed a splined tool to be removed from the hub, and carefully applied violence to be opened.
Don't know if a freewheel tool meant for another purpose entirely would just happen to be useful for cracking open a shimano freehub.
IME, the world of mechanics usually isn't that benign. But, stranger things have happened.