If explorer window is not maximized, hitting the "X" will not close the window, it closes each tab

Windows 10 - QTTabBar ver 1038

Try this:

imgur[dot]com/IgPL1JY.gif

1) make sure you have more than one tab open

2) make the explorer window any size smaller than maximized

3) hit the close window button

This won't close explorer, but close each open tab one by one.

Is this by design or a bug?

If it is by design, how do we disable it so the window closes?

I also notice this happens sometimes in a maximized window.

Thank you