(click on any image for much larger pic)
It's not a great pair of pics, but while there is a hex nut at the back, there's nothing pipe-like back there. Water comes from the meter, and water discharges downward at 90° from that dingus. Not at a 45° angle. Not out the back.
Mo posted a pic of a strainer: water moves through that in a straight line.
You posted a pic of a swing-check: water moves through that in a straight line.
Neither resembles what I see in the meter box, where water exits straight down.