It is the “weaver prone position” in the US Marine Corps Pistol Marksmanship manual. I assume you’ll take it that they know what they’re talking about?
Most ranges won’t allow you to shoot pistol prone as it involves shooting at an upwards angle onto a target set up at a ‘normal’ height. Thus setting up a situation where the bullet departs the range safety template.
Add me to the list that answered the question in terms of rifle shooting.
I’ve never even considered firing a handgun from the prone position.