So I have the two screens in front of me, and the ribbons look like this. The small one seems to connect at one point with the big one, but I don't have the courage to keep separating the two parts. Maybe tomorrow, if I have the time.
A USB cable has four wires. That smaller one has four wires. There's a small possibility that it's for a backlight, though. Honestly, the end of the big cable seems more important here (but I get your point).