"The exact number of digits you need to know isn't relevant"
The number of digits doesnt matter but CVV vs. no CVV does make a difference. CVV is the way to verify that you are allowed to use the given credit card number (its actually the second V in the initialization).
CVV is completely separate from the way the credit card number is generated. If someone else has your card number and CVV it implies:
Either your numbers were stolen directly from your card or your information was stolen from some third party server.
If your information was stolen from, say a merchant's server, it implies that they did not properly encrypt your credit number and that they stored CVV which should not even be in their database to begin with.
The number of digits doesnt matter but CVV vs. no CVV does make a difference. CVV is the way to verify that you are allowed to use the given credit card number (its actually the second V in the initialization).
CVV is completely separate from the way the credit card number is generated. If someone else has your card number and CVV it implies:
Either your numbers were stolen directly from your card or your information was stolen from some third party server.
If your information was stolen from, say a merchant's server, it implies that they did not properly encrypt your credit number and that they stored CVV which should not even be in their database to begin with.