Thanks for reading our review! It can be confusing, we're talking about two different types of resolution. The first is the pixel resolution of the HD standard, which you correctly point out is 1920x1080. All 1080 footage fits these exact dimensions whether you're shooting on a Flip HD camera or a Sony HDCAM digital cinema camera.
The second type of resolution, and what we're talking about when we measure it in "lines" instead of pixels, is horizontal resolution which measures how fine of detail the camcorder can capture.
Think of it like this, we have two books that are the exact same size (pixel resolution), and in one of the books the type size is quite large so you only get a few paragraphs on each page. The other book has a much smaller font, so you can get twice the amount of text on the same size page (horizontal resolution).
Hope that helps,
JB
John Burkhart
Editor-in-Chief
Videomaker