In Denmark, we do the opposite. It is common to make sure your baby sleep with their heads to different sides, so their skull won't be asymmetric or flat on one side.

I've also heard that other cultures, like the back of the skull to be flat, and keep their babies head from turning with well-placed pillows.

If you don't mind me asking, where did your grandfather grow up that that was a thing?

Either in South AL or Northwest FL.