Errrr the game was designed at 30fps and works good on it, and the GPU was powered up, not the CPU. So there isn't much point in making it 60fps instead of 4k. Are you complaining for the right reasons?

ALL ABOARD THE TODD TRAIN!!!

No. No. Gribble. NO.

That's only how checkerboard rendering works. It's the same for Horizon Zero Dawn for instance. I have personnaly pixel counted still gameplay images of Horizon Zero dawn using checkerboard rendering (so 2x 1080p or ~1500p) at 4k native. 

- VizionEck (Native 4K@60FPS)

Isn't that vapor ware? 🙄

that's the game we should be talking about

You almost made me spit out my coffee PB. 

- Futuridium EP Deluxe (Native 4K@60FPS)
- forma.8 (Native 4K@60FPS + 8xMSAA )

Added

- Thumper (Native 4K@60FPS)

It also looks like Hustle Kings supports native 4K but I'm waiting for verification.

I don't think this is any different than the normal checkerboard rendering Sony et al have talked about.
That system alternates which set of pixels are "fully rendered" and which are interpolated every frame.
When the image is still, the previous frames' "fully rendered" pixels are still 100% valid, so result is full 4k image.

To be clear, Sony's actual requirement for PS4Pro games/"mode" is only for 1080p.
Plenty of devs have in fact stated they will be offering 1080p modes for PS4Pro.
No reason why they couldn't ONLY offer a 1080p game without Half-4K Checkerboard etc.
(halving the pixel output would allow higher FX, possibly FPS, etc)
That said, the power of PS4Pro is pretty much designed around Half-4K Checkerboard,
and that will most often be seen as best usage of the power boost, even when sub-sampled down to 1080p.
I do think it could do some very nice stuff for lighting etc on pure 1080p.  Looks like devs are happy to offer options on that though.

The CPU was upclocked by 30%.  
Which isn't enough for 30fps->60fps generally speaking, but is enough that "solid 30fps" isn't a concern as claimed above.