I would call that a bullet failure. When a bullet is pushed too fast, especially into an animal as big as an Elk, you sometime get what is called a "splash effect." The bullet completely comes apart and may only penetrate a couple inches. Never reaching the vitals, the animal runs off and dies, maybe. Thats bullet failure and I've seen it happen. {A follow up shot "in the neck" before the animal got away allowed me to view exactally what had happened to that bullet}
That guy that shot at that Elk, very well could have been right on, but, one starts pushing bullets past 2800fps + taking close range shots one will start to understand bullet failure, intimately. No, not every time with all bullets, but a lot of the time with the wrong bullets.
You won't impress many Elk with power, I admire how they can soak up "premium bullets" from so called "magnum rifles" like a kid with a bucket of ice cream. You get an appropriate slug through the vitals and you might impress yourself, he, on the other hand, will probably still try to MOON YOU. {show you his but}.