battlefield 4 is optimized for windows though tiled resources
You would have a point if most of the PS4 games were sub 1080p, the issue is that the target they are aiming for is fixed, and Sony wants their first party titles to hit that target. The machine is very clearly built with that target in mind, and in the future even when the engines get more demanding the optimization & tools will get better as well. The PS3/360 didn't hit the market with a gang of 720p games, only to see a massive drop later in resolution, what they ran from Day 1 is essentially what they run today, sub 720p but close.
49fps avg on a PC with max settings in 1080p, the PS4 is not running all the effects you'll find on the PC either.
If they had the time to optimize for the PS4, 1080p @ 60fps on a closed box should be possible. But, there would be drops, then again no game runs at a "locked" fps to begin with, even when they claim it's locked.
edit: and that CPU