I also should mention this demo isn't a recent build of the game. The demo coming out on the 18th and the demo being played here is the Comic-Con demo, which is several months old.
Resident Evil 6 has four demo builds to my knowledge. The first is the E3 demo, or the demo that people got with Dragon's Dogma. Next is the Comic-Con demo, which is the public demo coming September 18th. A further along demo was sent to press a few months ago that was a newer build of the game. And recently the first two chapters for each campaign outside of Ada's was given to press, though the build of the game was a bit older.
To place the demos in terms of development placement and improvements, the E3 demo is the oldest, followed by the Comic-Con Demo, followed by the recent 6-chapter demo given to press, with the most recent being the 'prelude' demo handed out two or so months ago.
However, the demo builds don't matter much now as review copies have been being sent out to publications already. But the screen-tearing present here is from an older build.
A slightly newer build (the 6-chapter one) has various videos on Youtube, but is like this:
http://www.youtube.com/watch?v=T5ECd__Van4