It's not tearing, it's just a slightly slanted picture, because the lines on the left (or right, depending on how you hold the iPad) redraw a tiny bit earlier than the ones on the other side of the screen.
[1] I can only assume the new iPad's LCD is more inert in some way? Smaller pixels, slower crystal?
On the iPad, on the other hand, there are tons of horizontal lines in a table view, for example.
Also, I thought about the 60 Hz thing, and I think high frame rate is a bit of a red herring. After all, the lines actually are slanted; the higher the frame rate, the fewer degrees they're slanted at the same scroll speed, but whether we notice the slanting is independent of the frame rate.