I think that a wrist is easier to break than a forearm, so if the wrist guard transfers enough energy to break an arm, your wrist would have been toast anyway.
As BigMountain and others have pointed out, protective equipment isn't always enough, but it's hard to think of a case where it makes things worse.
I told my kids, "Someday, you'll have kids of your own." One of them said, "So will you."
-- Rodney Dangerfield.