Bug in the + button

Notepad is set to automatically group windows. When I open a text file in notepad, the text file opens and I see the + button. When I click the + button, instead of opening a blank text file and add it as the second tab in the group, groupy opens the same text file in second tab. If the 1st tab is a blank file i.e., if I started notepad and blank file is shown and I click the + button, a blank file is created in second tab. Furthermore, the entire grouped windows are maximized automatically even though they were not maximized. The behavior appears to be that the + button is duplicating whatever is in tab to the left. I presumed the + button opens a blank new file. I tested with Microsoft Word and it does open a blank new word document.