The window background is causing a lot flicker during resizing

When using the D3D11 rhi backend on Windows, I can see an obvious black rectangle in the opposite side when I drag the left or top border to resize the window. It's the same when I drag the right or bottom border. The contents in the window will also "shake" quite obviously when I drag the left or top border, but there will be no more "shaking" when I drag the right or bottom border.

But if I change the fill color of the window (by setting the "color" property) to "transparent", and use a solid color rectangle to fill the window to pretend it is the window background, the black rectangle issue is totally gone! And the contents are not shaking anymore either!

This issue only happens on the D3D11 backend. The OpenGL backend doesn't have this issue. It happens on both Windows 10 and 11, so it seems it's not related to the OS version.

I've attached a very simple re-produciable project, please use it to test this issue.