In the real world, sometimes, people do get "blown off their feet" from being shot.
However, it is not the common belief that the energy of the shot does it, it is the body of the person shot that does it. It is a muscle action, call it a spasm, or twitch, or whatever. Sometimes the effect of the shot causes the nerves to "short circuit" resulting in a large muscle spasm, which can throw the body off its feet.
Usually when this happens, the direction is backwards (away from the shooter) but not always. It can be in any direction.
The movies love dramatic images. It's what sells tickets. The reaction to being shot with a shotgun has been ..embellished.. so much over the years, its now an parody of reality, and virtually expected by the un, and under-informed audience.
Cars don't explode into flames when shot very often in real life, but in the movies, it's rare when they don't.
And the USS Missouri doesn't go from 0-30knots in 30 seconds, nor would it stop on a dime and pivot around the anchor chain doing so. (I love
Battleship, its sooo much BS, its fun!
)