Perhaps this will help clear things up: once the brakes have been applied, there are essentially two things which can cause them to release: pressure surges in the train line which are great enough to trigger the accelerated release process (this is the one in which the cars essentially release themslevles and what the video is all about), and plain old brake cylinder leakage. The different between the two is that bottling the air misuses a system function while BC leakage is on an individual car baisis, which makes BC leakage a neglibile factor in brake releases (and which the video doesn't discuss at all).