Similar to LinkedIn's "verified" process, Porkbun uses a 3rd party: veriff.com. https://www.veriff.com/privacy-notice.

It appears that Veriff's data retention is set by their customers (in this case Porkbun). Porkbun's policy says that this information is deleted as soon as they have verified that you "pass." They aren't quite as explicit as saying that they require Veriff to delete it that quickly.

Unfortunately there's a giant loophole in Veriff's policies (emphasis mine):

  (5) Fifth, we store Personal Data only for as long as the retention of data is required by law, a contract *or is necessary for the provision or development of our Services or required for protecting us against legal claims.* At the end of the retention period, we shall permanently erase the Personal Data or anonymize it.