The last time I flew, it was not all lines, but just one "experimental" line, and it was not something I opted in to or signed up for or supplied a photo or any

The last time I flew, it was not all lines, but just one "experimental" line, and it was not something I opted in to or signed up for or supplied a photo or anything else for voluntarily -- everyone in this one line (which was just a "standard" line, not tsa-pre or what have you), you didn't have to show ID, you just had to show your boarding pass and then look into a camera until the guy said "good". Probably that second link you found.