I got a response by Nvidia Staff on the nvidia shield forms:
"
Android TV is designed for TV use, not PC monitors, so it supports TV resolutions which does not include 1440p.
That said, we have added a developer option to open up all resolution support. Inside devleloper options (enable this by clicking settings - dp - about - build 7 times) there is an option for extended display modes, enable it. Note that some apps don't work at non TV resolutions like 1440p so there are some compatiblity issues when you enable this. Also note that the main homescreens UI scaling from 1080p to 4k will be turned off so your icons will be smaller and more will appear on the screen in the launcher.
"
I have enabled this and it works.
2560x1440 144hz and other settings and color options
But, yea, some apps, like Apple TV app, don't seem to like it.
Even channels app, things are not aligned right.
I for sure know that QHD 2K tvs were a things for a bit, but were quickly replaced by 4K.
Wish i had knew more about this Android TV limitation, may have swayed me to look more seriously at 4K monitors.
it is also strange, since the Shield is advertised to be a Android Gameing council and to appeal to gamers. I would think that there would be more users hooking a Shield up to their gaming PC monitors instead of a tv, than other streaming box devices.
At least this good info for anyone out there that uses these stream boxes with a computer monitor vs a tv.
and no. i can not see any difference really in playback smoothness etc, when i switch between watching the same recorded tv program, in 60hz on the Apple TV, and the Shield at 144hz, same 2K res.
The Apple TV does just overall, look better.
Seems, for me, the usefulness of the Shield is at its all time low now.