Can you imagine willingly handing your phone to a cop?
Please read the article. It's presented there, and not even hidden away.
If he has a reader on his belt, you would still not need to hand over the phone, you would just tap it on his reader, which would then prompt you to agree to share the specific fields from the driver license that he needs.
I mean yeah, of course they could still demand your phone, they can also demand you get out of the car, handcuff you, search the car and take anything they find on the most vaguely worded suspicions, but there's no technical solution for that problem.