The IDF carry on an empty chamber. Watch their manual of arms with their Glocks and they are smooth and fast. I practice that way and often carry a j frame.
When the US military carried 1911s, condition 3 was also standard. Loaded mag under an empty chamber.
The IDF and CCW are subject to different circumstances. When responding to a terrorist attack across the street, you have time to rack the slide. In a mugging, the guy will generally be within arm’s length before you have grounds to draw. It will then be unlikely that you will have the time to rack, and you may need one arm to hold him off while you draw.