I finally was able to test out the bendiness of an iPhone 5 yesterday. I went into a reseller and saw a slate iPhone 5 (along with iPad Mini). I first tried to bend the Mini. It was fairly easy to bend about 1 cm corner to corner (non-diagonal). What I did was hold one hand on the top end, the other hand on the connection end. I used about 50% of force to do that (I didn't want to buy a broken iPad Mini). When I let go it sprang back. I didn't check if it was perfectly flat (the glass).
Next I went to the iPhone 5 tried the same thing (twisting motion). About 50% of force I am capable of. After I let go, I notice that when you look at the glass from the edge, one corner straight, other corner I could see it was bent about 1 mm. So I think what is happening is that the Aluminum memorized the last bent and is holding one corner of the glass a little higher (just 1 mm).
Now, I was actually surprised at the strength of the aluminum, until I realized that the integrity is actually coming from glass and the battery, motherboard and other things inside. Everything is fairly airtight inside, so when I was bending I was trying to bend the insides as well (remember, no air gap). But I think the glass is 1mm off either because the aluminum memorized and held it higher, or the battery or other components inside were twisted and held the glass higher. That is up to debate.
So all those pictures of the Aluminum coming off? The rest of the inside is probably stiff and straight, but the aluminum just memorized where it was bent to and stayed in that shape!