While this is true, forged test results or vet invoices can be discovered within weeks or even days, depending on how long the test takes, should a buyer receive a snake with IBD. The buyer can also open a dispute with PayPal or their CC company - "Item not as described".
OTOH a fake het may take months or even years to prove out, especially if it was purchased as a hatchling, leaving the buyer with little or no recourse for a refund by the time the deception is discovered.