Ground effect & downwash?
If you have less "downwash", I suggest you would have less lift, not more, from Newton's second law - less change of downward momentum to the air, less upward force on the wing.
How's this for size: the (above-ground) flow pattern when in ground effect can be described by replacing the ground by a mirror image of the wing and airflow. This flowing air at zero height speeds the wake air backwards, as compared with the flow pattern when far above the ground, thus reducing the slowing parallel to the ground/drag when close to the ground.
For lift: the speeding of the air behind the wing backwards, when close to the ground, as compared with at height, causes an increases in the flow rate over the wing, greater downwards mass flux, so a greater change of momentum and more lift. Also consistent with less slowing in the flow downstream, also consistent with less drag.