Mmm interesting. I prefer not having decapitations in but i'll see how it plays out in the game.
Then never activate that perk. Problem solved.
In fact it's not inspirated in Deadly Reflex since wasn't this mod who implemented decapitation in games, but still it's a good thing to have in Skyrim, adds more realism.
I remember that Beth admitted Deadly Reflex was one of the mods they got some inspiration from for combat (hence the shield bash), so it's relatively safe to assure they got decap from that mod, too.