Well, let us give a look to how animation works. As in any videogame, animation is first acted out by a real person and captured by a camera (even in the case in which the creators are not actually using motion capture software).  In The Sims 4 someone acts out the scene that the animator asks for and afterward that scene is re-created by animation software such as Maya (which appears to be the software used by the Sims creators).  When the animations are ready they are transferred to Swing (The Sims Studio’s internal software).  However, each of these animations is very complex and The Sims 4 will offer about 15,000 animations.  Now, how long, and especially, how much work would it take for the creators to go through each animation and set different heights? Too long and too much work as explained by the creators.  Therefore, let us forget about the Sims heights and focus on what we will actually find in the game.