It is certainly knowable that the identity on the credit card is part of the verification process and that it must match his own. If the name he entered wasn't his own, the verification would likely have been denied:
https://discussions.apple.com/thread/6238222?tstart=0
That's why I'm suspicious as to which name he actually entered.
In this case, it seems the two accounts used different names otherwise they would mentioned it already because it's huge evidence that the accounts are linked.
In the U.S., you can add authorized users to your credit cards, and they typically send you new cards that just have a different name, but for which the rest of the information is identical (same number, same CVV code, same expiration).
At least this was the case with the cards issued for authorized users I added to my Citi Double credit card account.
So you could have a single card number with multiple valid names/users.
That's why I'm suspicious as to which name he actually entered.