It doesn't. Because they just gotta ajdust their resize algorythm once. Not for every single model.
Don't call me a troll because you don't get something please.
For example an earpiece as simple factor each time it is used.
-The races. For the position. Which is fixed for each races.
-The character size.
-the character ear size if their is the option.
And that's it. With that they can chose the factor of their liking to resize by a % for example. But that is using the above thing. So in the end is "fixed" too.
If there isn't a model it is because an automatic code does the rest. As the race is created now. It is done and shoudln't need any modification unless they rework the race altogether.