When the weight is vertical the flap is also vertical/ “open” in the video. But when the system is all together that just means hot gas is diverted up against the bottom of the intake manifold to help with a cold engine. The valve “closes” when it’s hot, basically just diverting that hot gas down the exhaust pipe and away from the intake. A crude little system. It’s good to work the valve every now and then to prevent it from sticking. Lots of people over the years just stop messing with it and try to keep it stuck in the hot position.