Sorry to continue to harp on but, if it's still not clear, all of that unrestricted 'safe' pushing ever widens the gap between the force you are able to muster and the force you are able to control away from the machine when your stabilizers and support muscles are called upon to help and support in a real-world movement.
This is the part I meant about being an injury waiting to happen. Pushing some significant poundages on a machine doesn't mean that you can do the same to a free weight in the real world. A free-weight program will lead to a fuller, stronger, better-developed, functional body.