This problem appears in every win32 app, and it spread to WinUI 2.6 apps with Xaml Island. On my 4K screen, every win32 app and Xaml Island app maximized window title bar height will be 1mm thinner than the normal state, you can measure new file explorer on Windows 11. This problem is because Windows 7 has a border around windows, and when windows are maximized, the border will be hidden. But win10 and win11 hasn't border around the window, this logic still exists, so it makes uncomfortable and strang experience. Any Microsoft software engineer can mark this as a bug in Windows workflow? This is really an anoying design-bug.