Italia 458, howdy...
Oh yeah. I was not tracking with the op.
The easy way for me to explain it to myself is this:
At a constant AOA, the airfoil produces more lift in Ground effect than above it.
"Effect"ive AoA is higher. So it stands to reason the airfoil will produce its maximum lift sooner, maximum lift is produced at the Stall, therefore, the AOA (Stall) is lower in GE...
I also like the "pillow" visual.....