preta's is not a good analogy.
Without actually seeing the impact area, I'd hazard an educated guess that the 738 lower wing skin was nearly completely sliced into inboard and outboard halves by the legacy winglet (with a closure speed of 1500 ft/sec).
This means the upper skin, designed to carry chiefly compression loads (or minor tensile load if negative G), is now carrying a bending load from the lift of the outer wing. Being ralitively thin, it won't endure long. Ergo the lift load bends the outer section upwards, hinging on the upper skin in line with the cut in the lower skin.
Although I haven't seen the debris field pattern I wouldn't be at all surprised if the outboard wing didn't separate completely in the highspeed descent.