That’s news to me, too. Makes sense though. I assume it’s because you can drag tabs from one window to another. So if you open two incognito windows and drag on

That’s news to me, too. Makes sense though. I assume it’s because you can drag tabs from one window to another. So if you open two incognito windows and drag one windows’ tabs into the other, the browser needs to decide what can be shared. You could keep their states separate, but what if you then you open a new tab in that shared window? What state/profile object is the new tab associated with? Just sharing between all windows is easier to handle.