Exactly as most are asking for email which inadvertently can confirm the identity and if you use the same email for other services, they can get even more data about you. I guess it's a matter of trust, how much do you trust their 'opt out' promise.
I guess we're lucky that most of these SEO-saavy brokers seem to at least pay lip service to US/EU laws (or even do so voluntarily, since I think only a handful of states actually restrict selling your publicly-available or personal information online).
I shudder to think about what's floating around for sale on the dark web or companies hosted in countries that don't care about US law.
If this worked then anyone could opt out anyone else, which some people would object to. I think that's the loophole they use to force you to provide even more info.