IMO the grip safety is no safety, when the gun is gripped to pull the trigger it is really difficult not to engage it. If the gun is dropped on the muzzle and there is not a firing pin safety the 1911 can fire from the inertia of the fall. Grip safety will not stop a ND in that scenario. If the finger is on the trigger and the thumb is wrapped around the grip well that is no safety. The only time I see the grip safety actually operate as a safety is when the 1911 is carried in condition 2. To cock the gun the grip safety will return to the position to block the trigger.
The thumb safety is useless if it is off, when it is on even if it fails the hammer has a notch that will stop the hammer from moving fully forward. The only way the gun is going to fire is that the safety is off. I have not seen or heard of any ND with a 1911 with the safety on. ND's are caused by negligence, plain and simple and safeties will not prevent this. Nor making claims it cannot happen because I guarantee that every person who has had a ND has claimed it can't happen until it does.
IMO the safest handgun is the one with NO safeties, such as my SA revolver, which is why I carry my 1911 in exactly the same manner. I have never had a ND, there is only one way to fire a SA revolver and it is deliberate. The hammer is not cocked until the gun is on target period. I have nothing against condition 1, but the illusion of safety is just that, an illusion. If the user has a brain fart and trips the safety, and grips the gun, and puts the finger in the trigger guard, it is likely to result in a bullet in the leg or arse. It won't be the holster's fault, it won't be the guns fault, or failure of the safeties. It will purely be the fault of the person who pulls the trigger.
One of the biggest problems with inexperienced 1911 users, is while getting "used" to condition one carry is playing with the gun. A big no no, plus almost every condition one user I have seen grabs the gun, flicks the safety, and as soon as the gun clears the holster the finger goes in the trigger. I am not accusing anybody just what I have seen. It is the same problem with glock users, or any other person that is getting comfortable carrying using poor gun handling habits. If a person is going to carry condition one be damn sure what you are doing, a gun is not something you get used to, or I should say get complacent. If you do not have the skills to confidently carry condition one with a 1911 it is a good way for a aww poop. Train, train, train please don't endanger others with inexperience and the illusions of safety.
It is a gun for God's sake, it was meant to throw a hard object very fast. Keep the hands off the gun unless needed and the fingers out of the trigger guard until needed. Put the safety on, and leave it on don't keep thumbing it, or you will screw up sooner or later.