At least then the only elbow you can blow off if you slip will be your own.
(Seriously: Go grab your blue gun and game this out for yourself. I am aware of at least one person who gave themselves a spectacular "racing stripe" and missed winning a titanium elbow by a tiny fraction of an inch in this manner.)
Yes, but it starts off with the elbow in front of and just above the muzzle.
I mean, the consensus these days is that the old-school "pinch check" is a little too unsafe because it puts a finger in front of the muzzle; this "across-the-body slide rack" puts half your arm there.
Sure, if you do it right, you keep your forearm and elbow above the bore axis and your finger out of the trigger guard, but since it's possible for practically anybody to run the slide while keeping the muzzle properly downrange, I just fail to see the purpose in propagating one with such potentially disastrous consequences if you fumble it.