Qube, on what platform did you observe this? On Windows I do exactly that with one of my apps. I noticed nothing of what you describe.
Windows & iOS.
To replicate the issue (will post example when I have time) :
1.. Draw a dark yellow (or blue, red etc) circle in your favourite image editor (must be antialiased and 50% opacity)
2.. In GLB have a simple 3D skybox (darker the better)
3.. switch to 2D and using POLYVECTOR draw that circle on the screen at different random location. You'll notice that it's not perfect as pre 10.118 versions were.
LOL, having read that back it seems a little overkill to show something broken so I'll whip up an example with screen shots later