If there are a lot of playback devices, and the default/selected device is far enough down on the list and/or there are enough programs displayed under it, it will usually only show some of them, requiring scrolling to see all of them. It should always show as many of the apps for the active playback device as possible (all if they fit on screen, otherwise as many as will fit). This can be done probably best by simply auto-scrolling the list to show them all (should probably scroll to the point the next audio device's header is at the very bottom, to make it clear all devices are showing, unless that would push the current audio device's header off screen at the top, in which case that should be at the very top). It could also be done by collapsing the other devices (which ideally should be able to be manually individually collapsed, perhaps another issue), but that's probably not as good a solution.