Yeah.. the preview pane appears to want to wrap any text it can. It even wraps the text in a Word document that has a graphic that the text normally fits inside, so it ends up flowing out the bottom of the graphic. It's obviously just meant to give you an idea of what's in the file rather than actually make it legible.
Edit: It is scrollable left & right, but only because of the graphic. The text is still made to fit in the preview pane width.