Strange as the mouse icon doesn’t fade with it, I suspect this is some weird software effect, or the mouse icon does fade, but the camera didn’t capture it so well.

Or there is some complex failure modes changing the grayscale on those particular rows of pixels, so black and white looks OK, but the in-between colors scale down.

Update:

After turning up the video quality, it appears that there is some delayed fading and image retention on the failed area, so this is related to some flex cable or row gate IC issue, only affecting these particular rows.