You are ASSuming that the catastrophic arc flash happened AT the probe leads. What can, and does, happen is that something relatively innocuous happens first, like the probe leads vaporizing or the meter exploding, and THAT spews out metallic "mist" and/or ionized gasses, which then propagates a LARGER arc flash event. All of this can happen in a tiny fraction of a second.
Originally Posted by the blur
"Dear future generations: Please accept our apologies. We were rolling drunk on petroleum."
— Kilgore Trout (via Kurt Vonnegut)