How do they get your data removed from the brokers' databases?
This was my instinctual, cynical assumption, too. Unless there's a GDPR-like law in place and some standard for differentiating identities, they're just going to find loopholes to recapture peoples' data (e.g. remove middle initial, modify address format, etc.).
"If you are located in the United States and have a Monitor Plus subscription, OneRep receives your first and last name, email address, phone number, physical address and date of birth in order to scan data broker sites to find your personal data and request its removal. OneRep keeps your personal data until you end your Monitor subscription in order to check whether your information shows up on additional sites, or has reappeared on the sites you’ve already been removed from."