This is a picture of a black halftone full screen @ 50-60% black. So a solid grey. I didn't bother to match it's true colour but no bar seems to appear.
One thing i noticed. When opening this image fullscreen... my screen flickered a bit once opening full screen 'to readjust itself' but then stays stable. (at the top of the screen)
I don't see this as a problem. Grey colour is hard to output. So long as it ends up staying consistent.
Maybe we should all start disregarding problems on solid grey light output.