They say they don't want Ps Pro only games but ultimately if the Pro takes off they don't have a choice.
I'm sure a dev could have their game "run" on a PS4 Vanilla. In 480P. With wireframe graphics. At 15fps.
It won't go quite that far simply because there isn't that kind of difference between the two machines but running on a Ps4 and "Running in a way that you'd actually want to play the damn thing" are two very different concepts.