I've noticed that the new sprint animations for weapons only work if the weapon doesn't have a grip. At least for the rifles. I'm really glad now that the sprint animations have been made to match the footsteps of your character, its really an awesome improvement. Not sure if this was overlooked but its worth the question.
On a side note the new gun position for HC Checkpoint while sprinting seems very odd for someone wading through molasses. Thats just IMO tho.