The change to allow multiple Unity windows in the taskbar and alt+tab menu allows the user to select the window to open but doesn't actually activate that window and the last active view in it. It just activates the Unity app and whatever window and view was active before.

Repro:

1. Start the Unity editor.
2. In preferences, enable the option to show secondary windows in taskbar (last item under "General".)
3. Restart the editor
4. Break out a tab so there are two windows.
5. Alt+tab to the other window - or - select the other window from the taskbar preview

Result: Unity activates, but the last active window and view becomes active. Not necessarily the window the user tabbed to.
Expected: The window that is tabbed to or selected from the preview should activate and its last active view given focus.