Please note that I'm not reporting a problem:
I have a Geforce 1080 @ 4K, drivers 24.21.13.9764 (ForceWare 397.64)
This is what it looks like while having 60fps, and basically just spinning the camera in the inn.


This is what it looks like at 2560x1440 like one of the posters above, again at 60fps:


Please note the blue PerfCap reason while at 2560x1440 and compare it to the grey/green with 4K. While at 4K it's throttled due to Util/Pwr because it crosses the TDP threshold, and is why it typically runs at 50-55fps. At 1080p and 1440p it's only at VRel (Voltage Reliable)

So, basically it should not be maxing out the GPU at 2560x1440 even under maximum if it's at 60fps. Something else is amiss.