You too, have misunderstood.
The recoil INITIALLY wasn't just missing. It was only missing after they removed it in a patch. Before, it was broken: like an MP7 is pinpoint accurate when crouching, while an M13 has 6x the recoil it has normally when you were crouched. It is obvious there was some sort of coding issue with the modifiers the stances were supposed to have.
Try reading these two comments especially:
Only AFTER these broken recoil patterns were discovered and gained significant publicty on reddit, they removed them. By adding a small, stowed away line at the bottom of the patch notes that just casually stated "Crouch and Prone no longer adjust recoil".