Games can get away with claiming "4K" and "8K" through clever rendering. Only some parts of the screen need to be rendered at a higher resolution at any given time. Tomb Raider shows this off a bit. When geometry is far away and DOF blurs it, it's also being rendered at a lower resolution. It's like how the human eye doesn't gave a strict "resolution", but instead has higher acuity at different spots of your vision.