The risk is not that the site would insist on attestation, it's that Apple would volunteer it. They could pass an ID through that channel, use it to strike up a separate conversation which makes them some money, informs Palantir about what protests you've been to, and the service in the middle gets a finder's fee.

If we want this to be usable by consumers we need to prevent this kind of thing, not thank Apple for their restraint.