It isn't as easy as it sounds. It's a lot of fingerprinting, location, and metadata aggregation from an astounding variety of sources that is extremely difficult to fake - It can pinpoint you to an astounding degree. I have been working off and on the last 3 years in the privacy space (passion project) on a similar concept of adtech data obfuscation, and it's far more complex than just "put a fake birthday in a form" (although stuff like this can manifest in interesting ways).