[Number 3]

I believe the real reason is the same as why you can't deactivate your airbags.

If you use AFM to get your EPA certification then you have to leave it and the programming intact all the time.

You could tie AFM to an ECO button that allowed the customer to select a more ECO friendly calibration. That is quite easy to do.

But with the Camaro for example AFM was needed to avoid the GG Tax otherwise you'd have the LS3 in the Automatic as well. So in this case you'd be cheating the government out of revenue.

Again, easy to do. But you would have to live with the lower EPA number and maybe worse, the GG Tax.