I'm reminded of the settlement with Facebook where it was illegally allowing racial targeting in ads for housing, which is illegal [1]. If platforms were suddenly liable for allowing or failing to stop the targeting of minors, they'd suddenly have a lot of incentive to figure this out.
The beauty of this is that they already do it. Your profile with FB, Google, etc has a lot of implied demographic information based on your activity because they want to sell audiences with certain demographics.
As an aside, whenever I see "think tank" my first question is "who is funding this?" and I learned something I didn't know previously. In the UK, these bodies often aren't legal charities. Instead they are non-profit companies limited by guarantee [2]. One consequence of that is that they don't have to reveal their funding like a 501(c)(3) would (and, yes, US think tanks are generally 501(c)(3)s).
I didn't see any obvious red flags in the trustees for Foundation for Information Policy Research for what it's worth and it's an almost 30 year old organization.
[1]: https://www.justice.gov/archives/opa/pr/justice-department-s...