Actually adjustable headrests may offer less safety for the passengers. For the back seat passengers, they are rarely adjusted properly, and are often removed. Other makers, such as Volvo (a rather safe car) also have fixed headrests in a number of models.
While you're at it, headroom should also be improved by an inch or so (in front and rear). That's the downside of having the battery in the floor of a vehicle that has aerodynamics as one of its first priorities: Vertical space is severely limited...