Go read how the meter valve works. Very low pressure it is open. It is also called a delay valve. As you apply pressure the valve closes and HOLDs off pressure to the front, while pressure builds and applies the rear brakes first, then it opens again So there is a range in which it is closed, then it fully opens again. This prevents a tail spin when braking in rain, snow. Read the whole training document. Stop picking single sentence out of context of the discussion. Plus we were talking about distribution block cutting off flow, which it does not do.