We've also seen a finishing move on a human warrior in the demo while dual wielding swords. This finishing move however didn't jump into third-person when activated. Either it's specific for certain monsters only or you can get an option to toggle the slowly/3rd person off for a normal speed/1st person kill, the exact same thing you could do in FONV basically.
If this is not the case i will be truly dissapointed.
It has been confirmed that finishing moves are different for each weapon and each creature. In the demo we saw forced third person and first person finishing moves, so it's very likely that those were dependent on that specific weapon for that specific type of creature/enemy. Finishing moves are also not optional (based on what we've been told so far) because they are automatic and you have no control over them.
Hopefully finishing moves will be optional kind of like in FONV. One toggle for slow motion, one toggle for forced third person, one toggle for the entire finishing move feature. Perhaps they could even be connected to perks (and thus save us from the horror of having too many toggles), if some kind of extra damage bonus to using finishing moves was added to the game.