[swarmee]

One thing to note is that PSA's registry catalog is not perfect. People that sign someone else's card will be counted as the player on the card. So if Roger Maris Jr. signed his father's cards, they would still show up in the PSA/DNA tab as signed by Roger himself. It also fails to account for all the cards signed that only go through autograph authentication (formerly blue flips), because PSA is not authenticating the card.
I'm sure there are also a bunch of counterfeits that are in the DNA pop report from the red flip era before dual grading when they were not authenticating the card, but they may still show up in the pop.