I know the comment you're replying to called it a "180 degree hinge", but the linked Ars Technica article states that it "flips around to the back with a flexible hinge, a la Lenovo's long-running Yoga design". This is not clear from the pictures in the article, but was on display during the livestreamed event earlier today.
It's sort of obvious if you've seen the Panasonic implementation like in CF-RZ line, it's the same setup. The top and bottom halves are connected through a pair of square pieces long as the laptop's thickness. Hinges each articulate 180 degrees to total 360 degrees to allow it to fold like a human knee joint.
The four hinges must stay synchronized under lift force from the user, but I haven't seen that being a problem on a Let's note, so it's probably good.
