For more info on what happens behind the scenes when used, at least from what I've seen online, the Digital ID has the picture taken of the front & back of the physical ID along with a Live Photo of yourself to match against. This is verified and then encrypted, so the only time that info is available to anyone ever is if they actually scan the iPhone with the ID listed. Then they see those same three pictures to verify you, and if needed, to also scan the Bar Code on the back of the ID. In theory, it does setup a way to just never use your physical card again, but nah