Even if it is a bool there is probably an extra factor: Liability in case there is an fire or other incident. Tesla probably on its side reduces it's cost as well, by only insuring (be it by having cash reserves or actual insurance) it's liability only for the cases where it is enabled.
It's of course hard to prove as cause, but if there is a liability case it might become "interesting"
Edit: Also relevant: even without incident, the disabled heated chairs may be broken. By not being enabled Tesla doesn't have to repair them under warranty as the aren't a feature. Thus they maybe can reduce quality in the production
Isn't it rediculous to assume a seat-heating feature could cause a fire? I would assume there are even hardware limitations in place to prevent heating that would otherwise cause damage.
I imagine the situation at court "you implemented combustive seat-heating for this model?¿"
If the hardware for the feature is present and hooked up, and the software (if any) that's needed to run it is installed, then it is indeed "just a bool somewhere".
If the hardware requires non-trivial software to enable the feature, and that software is not provided with the device, then it's fair to require additional payment to buy that software. But also no one should be able to prevent a third party from reverse engineering the hardware and writing their own software for it.
I think "who gets to decide?" is a somewhat silly question. It's the same answer we'd accept for just about any situation: someone reasonably well-versed in the technology.
It's of course hard to prove as cause, but if there is a liability case it might become "interesting"
Edit: Also relevant: even without incident, the disabled heated chairs may be broken. By not being enabled Tesla doesn't have to repair them under warranty as the aren't a feature. Thus they maybe can reduce quality in the production