Focus always and exactly follows the mouse cursor, regardless of whether the window under the cursor is a new window.
Currently, using "Mouse Focus" with "Focus New Windows" unset, if a new window is created under the mouse cursor, the new window will not have focus (despite the cursor being over it). This window would have focus in the new model. Otherwise, this model is identical to "Mouse Focus" with "Focus New Windows" unset.
This option/model should probably be mutually exclusive with the "Focus New Windows" option.