That being said, if you scroll through thousands of these, what you are saying does happen often, but even more often, the faces look completely real and I would have no problem believing they were anything but.
Maybe I missed your point though....
I suppose that depends on who the viewer is. For example, everyone at work was blown away with how hard it was to pick the real face here: http://www.whichfaceisreal.com/index.php
However, I went through about 50 in under a minute and got every one correct.
Programmers spend their time thinking in abstractions and models, rather than appreciating things as they are, as an artist must (see Drawing on the Right Side of the Brain -- https://www.drawright.com/theory). I wouldn't be surprised if more artsy types have a much easier time recognizing these fake photos, despite all the component pieces roughly being where they should be.
I wonder what causes it.
I don't know why it's so common to have an arbitrary nonsense "sticker" on a face though, I wonder if it's because input photos were trunacted at edges and the learner tried to model the edge as a facial feature instead of pruning it's knowledge to a safe interior of the photo.