The problem with your hypothetical was that you casually introduced the police as an enforcement mechanism for cases of a minor accessing an over-18 website. The implication is that the physical police are now involved in our access of websites, and you’re saying the tokens involved in us accessing websites will have some evidence that they can use in the investigation of that access.
This is why we keep saying that the anonymous token schemes don’t preserve privacy. It always turns into a slippery slope of adding escape hatches to the anonymity to enforce violations. The very implication that the police are going to be tasked with going out and confiscating devices to investigate suspected age token violations is an indicator of how far the window has shifted on Internet privacy.