

Problem is they aren’t required to prove it to you - some witness - unless it’s your child that’s involved, and they can take their sweet time providing proof to the person being detained as well, waiting until they’ve already thrown you to the ground and cuffed you.
In theory the unique id produced by the scan could be salted by you, uniquely for each website or application, and then provided to the site. This would keep aggregators from being able to track all your activity, or at least it would if they didn’t already have fingerprinting techniques that do it without the need of another unique identifier.