How are they confirming anything? They're literally just confirming that someone who clicked that link owns that number. I'm not sure how that's confirming an identity linked to the phone number. If I click that phone number and I have information in there for John Smith and Adam Jones how does this contribute to them knowing whether they're seeing John, Adam, or someone else?

Like I said, it's a data point. I don't think it fundamentally deanonymizes the number (not that it's even anonymous to begin with). Instead, it:

* Confirms that a number is a live subscriber;

* If there are N possible identities tied to the number, it strongly suggests that the most recent one is the "current" one;

* Links my phone number to a browser session, which provides further information.

Edit: It also fundamentally turns a passive source of information (a DB of phone numbers, of unknown quality) into an active one (people are actively confirming that some of these numbers are real and currently subscribed).

Hypothetically if your assumption is correct, this is the most expensive way to collect this information since there are dumps of data available on the dark web for pennies, while these queries are 100X more expensive. Criminals are trading this information without your permission and exploiting it. We just wanted to create a tool to create awareness