Alt+F4 shortcut does not 'exit' but closes current window. (RC10)

With the Scrivener for windows v3 shortcut-theme loaded, The behavior of Alt+F4 is not to exit the program, as expected, but to close the current window. This can be a windows-thing.
When ‘show template chooser when there are no projects open’ is selected, closing the current window (if that is the only open project) will go to the template chooser; exiting will really exit the program. Alt+F4 will not exit the program if ‘show template chooser when there are no projects open’ is selected.

To make things more interesting: Trying to assign Alt+F4 to ‘exit’ in the shortcut-settings dialog by using the ‘record’-feature causes the settings-dialog to close, without any changes made. It looks like ALT+F4 is hardwired in windows.

I can reassign ‘exit’ to e.g. a CTRL+ALT+F4 shortcut. In that case, when using the shortcut the program is really exited and the template-chooser does not appear.

By the way, a real exit is almost instantaneous, a close of the last project, causing the template-chooser to appear causes a noticeable delay. Is building this template-chooser so time-consuming?