This is not to defend the government or support any disgusting measure like facial recognition to control the masses but maybe the way to opt out here is more complicated. The only reason why they can use the tech for facial recognition to compare you with your passport picture is because your face was already scanned when you applied for the passport. The biometrics of your face are already in the database that those machines are using. You could argue that you are training the recognition system, but it is already being trained with other cameras.
If you really wished to opt out you would need to wear some type of mask all of the time (I am not suggesting to do that) and you should travel only by car, train and ship.
If you go at the passport control with a police officer there is a camera there as well, collecting your biometrics in the exact same way. The only real difference is that the officer might ask you additional unpleasant questions.