Yes. I do have knowledge about this since I fly Delta internationally a lot from the USA to Ghana and Delta always requests you show credit card for locations like Ghana with reputations for fraud.
If you buy it from the Delta website, it alerts you about the requirement and you have to click a check box in agreement before you can purchase the ticket so you’re aware.
If you bought it from Expedia however, it’s Expedia that makes the payment to Delta and thus you’re exempt from having to show the physical card.
If you’re still uncomfortable after my explanation, you can also go to a Delta office any day before the persons flight and show the card. I did that when I purchased tickets for others directly from the Delta website.