We get the warning in the following chain of events is:

• using wayland with a scale that isn't an integer
• close the window with the icon.

This triggers:

• QWindow::close which calls setVisible to false, triggering a queued exposeEvent marking the window as hidden
• QWindow::destroy which kills the platform window
• we process the deferred (in)exposeEvent
• without a platform window we go into a fallback based the screens
• On wayland, we don't have accurate information for screens with floating scale accuracy, only a legacy int, so it shows as a change.

This seems to happen on most windows.

In a sense it's a false positive, because if we didn't have the QWindowPrivate::get(window)->updateDevicePixelRatio() line, we wouldn't be detecting a stale value.
We also don't care about the DPR when the window is inexposed.