Quick tl;dr
"The first hurdle for instantly revealing anyone’s freeze PIN is to provide the person’s name, address, date of birth and Social Security number (all data that has been jeopardized in breaches 100 times over — including in the recent Equifax breach — and that is broadly for sale in the cybercrime underground).
After that, one just needs to input an email address to receive the PIN and swear that the information is true and belongs to the submitter. I’m certain this warning would deter all but the bravest of identity thieves!"