The area in the city where he notices the usual (and very noticeable, even in a compressed 480p youtube video) CBR artefacts is one of the most GPU demanding spot on base PS4 in the city (I know this because the PS4 fan could get pretty loud on this spot). And I definitely have only pixel counted 100% native 4K images with no reconstruction and zero artefacts.
I think the game switches between native 4K and CBR 4K depending of GPU load.
That would actually be clever. Probably a lot less noticeable than dynamic resolution.