Green region in viewfinder on Microsoft Surface Book

Green region appears at the bottom of the viewfinder on Surface Book. Couldn't be reproduced on Surface Pro nor on other random devices.

The screenshot is taken with UWP build of Qt 5.12.0.

The green area is not present in captured images though and those captured images only contain the visual part (not the green region), which could point to the fact that it is just padding to keep the aspect ratio. It also changes its size if the window is resized which would point to that.

This green region does not occur with non-Qt applications (Skype or Windows Camera), therefore I suspect this is a Qt issue.