this was the same play book with milliliter wave scanners, which are now proven to not be completely safe but who cares. at first you could opt out. then opt out was the same as mandatory patdown. then opt out meant an extra 30min wait by the xray scanner... etc. now its fully not an option.
meanwhile i bet the 911 hijackers would have zero problems getting pre check or whatever other private scamer is selling the no-scan boarding these days.
lastly, yeah, this is totally so they do not need a warrant to unlock your phone if you have face unlock. in the most plain and obvious Kafkaesque "he did provide the facescan willingly your honor. not once he opted out, which was always an option".