Mine is iMac 5K with M295X. Just did a fresh install of Windows 10, with latest Boot Camp 6.0 downloaded using Boot Camp Assistant. Still no 5K on Windows.Very disappointed.
Who's fault is that do you think?
I think they fuse two displayport 1.2 pipes using the TCON to deliver the 40Gbps of bandwidth required for 5k.
What screen resolution do you get with Windows 10?
3840x2160
Is that the maximum resolution on offer? Can you set the display to 5120x2880 or reduce it to 2560x1440?