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.
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.