Recently I tried using the horned tiefling head model for a character, and when I entered the gameworld I instead ended up with the "standard" nr 1 head model.
At first, I thought I might have just made a mistake. And tried testing it by creating yet another character with which I was sure to use the horned head for but ended up with the same result.
So then I thought, perhaps this head model was supposed to be usable only for approved tieflings, but even after my character got wanded for the subrace, I could not set the appropriate head with the setheadset command. There was simply an empty gap between headset 19 and headset 21, and I strongly suspect the set 20 is the one I needed.
If I recall, I had to have DMs set my head and tail options manually on their side with just about every tiefling I played. (which is a few)