> Thus failing Microsofts own 'Windows Certification' then?
He's right, you know.
The Close button on the title bar should have the same effect as the Cancel or Close button within the dialog box. Never give it the same effect as OK.
I am not sure he is, even though I would class it as a dubious move.
This is not the normal nagware to install Windows 10 but appears to be the notification that it will be installed.
There is no "Cancel" button, only a link to change the installation date or abort the installation.
Closing the form is accepting things 'as they are'.