It would have been an offhand shot at an animal that was bedded down. While I'm a pretty competent offhand shooter, I would have had to expose more of my body to do it. Also, I needed to carefully glass the animals to make sure I didn't shoot a buck. Notice the doe had 4" horns.
Pronghorn are much more skittish than deer, elk or caribou, they will get up and bolt at the slightest movement. Then, I would have been walking the prairie again instead of dressing game. The belly crawl worked (and there weren't any cactus or rattlesnakes along the way).