It uses checkerboarding to achieve that result.
Contrary to what the new video released for David Cage and Quantic Dream’s upcoming Detroit: Become Human might have suggested yesterday, it seems like the game will not in fact be native 4K on the PS4 Pro. In a statement since released by Sony, it has been confirmed that while Detroit will hit 4K on the PS4 Pro, it will only do so via checkerboarding, and not natively.
Now, this is something that most should have (and probably did, before yesterday’s announcement) expected all along—the PS4 Pro is a wonderfully capable machine, but it is not capable enough to run high end AAA games in native 4K. That said, Sony’s teams are wizards, so there was always a chance that they had somehow managed to pull it off with Detroit after all.
Even if Detroit: Become Human doesn’t end up being native 4K, however, it looks great regardless, and should look great on a PS4 Pro even with checkerboarding.