The software’s ability to properly identify people is nowhere near as good as they would like you to believe. I’d encourage you to read a book called First Platoon to see how often these systems fail. By forcing you to insert your ID into a machine and then matching your face, they are trying to train the identification techniques. There is a reason it is optional and not actually used to identify you.
Discussion
It's optional because they're patient for the tech to catch up (it will), not because they're respecting your rights.
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.