Or, one Glock SafeAction system, if you wanna use their name for the 3 working together.This is (drum roll please...) incorrect.
Glock firearms have a trigger safety, a firing pin safety and a drop safety.
That's three. Not one. Three. Three is more than one. It's actually three times as many as one.
I know some folks have concerns with no external safety on handguns. The biggest danger with the Glock SafeAction system is that if anything crosses that trigger, it can be enough to allow the trigger to move. If the trigger moves back far enough, the gun is gonna go BANG. There have been documented cases of trigger drawstrings and other stuff doing the job. You can reduce the risk with a heavier trigger spring assembly -- but it's still there.
That said, I'd still like some actual documentation rather than "someone says so." And, if it were necessary, a manufacturer could easily incorporate a manual safety on a striker fired handgun... If it made the difference in getting the US military contracts and not... Yeah, I bet it'd be done in a New York minute.