Hmm.. the 3 stamps I have on my amendments/endorsements page are all from PVG. In fact, China in general tends to stamp all over the place- The only stamps that properly fit the space given are the Chinese visas I have (half my visa pages are filled with Chinese visas) and my arrival at NRT (and while I appreciate the effort the BKK people made they still stamped over the edge of the page on departure). And it's impossible to screw up the visa placement because it's full-page. But that's just my personal experience. And I've never heard a peep from ORD as I re-enter the US.