Well i didn't found anything to change the Head tracking for the player. I tried to add the line from the Fallout ini to the Skyrim ini without result, so i checked the CK and there was an option "Uses Head Track Anims" but it doesn't affect the Player. So i think it must be something hard coded.
It didn't work in Fallout 3/NV either. It still works for NPCs, just not the player character, so it can't be disabled for performance reasons. If a NPC encounters a corpse, or any object of interest, they'll look down at it as they go past. In Oblivion the player character would too, but from Fallout 3 onwards it's been disabled and the player model just stares blankly ahead like a mannequin at all times, uninterested in the world around. I don't know if it's a coding oversight or deliberate, but I can't think of any reason to deliberately zombiefy the PC.