On some machines set up the way you describe I'll intentionally do a post catch, ball comes down the lane I'll hit it against the sling with the intention to trap the ball. If my timing is off this move can turn into what you describe, a live post pass. A skilled player could regularly do a live post pass, but there are other, safer, ways to accomplish the same pass. Practicing live post catches would be worth it, I wouldn't spend a bunch of effort into learning how to live post pass.