At the time it was claimed (probably true) that it was necessary to go to this length so that PayPal would honor the transaction. PayPal is notorious for charge-backs, and with the Bitcoin seller having followed these procedures to verify e-mail address and phone number matching the primary on the Paypal account that was buying bitcoins, the person could claim and prove that they indeed sold something. Without that verification, PayPal would almost universally reverse the transaction at the request of the buyer.
I haven't bought or sold any bitcoins with PayPal in a while, I don't know if people are still doing it or if it's again considered a "hot area." Last time I heard anything, sellers stopped accepting MoneyPak because it's usually 100% reversible without cause by the buyer. It's likely that in the current US climate, most buying and selling will have moved to formally built exchange websites and even that nobody will be selling coins anonymously in the well-known #bitcoin-otc community. You'll just have to find someone you know and trust, or can personally identify, in person, and (take their/give them) cash.