It's optional because they're patient for the tech to catch up (it will), not because they're respecting your rights.
Discussion
Correct. They gotta train the systems first.
You walk from the airport doors to an assigned seat and then sit there for hours. They're recording & training and probably have been since 9/11, not sitting on that footage, waiting for your consent.
The whole "you can refuse the headshot" thing is a weak platitude.