Which would only be helpful in my example if the defense lined up with three D-backs in a cover-3 before the snap, which would be...unconventional.
Most teams line up like normal with the two safeties deep, and then either drop a safety underneath and two corners deep if it's a cover-3 'sky', or roll the safeties over and drop one corner deep if it's a cover-3 'cloud'. Regardless, those movements happen after the snap.