alt Hacker NewsRe: YouTube example, the issue (as I understand it, and I'm what you could describe as the opposite of an expert in that) is that the video and the playlist blend with transparency over one another. Had the playlist appeared sliding from the right side of the screen, it would have worked (I guess).
yes what you described is how it is right now on youtube, the main reason is to make it look more fluid and natural, apple examples shown mostly work because the overall structure is very static and have a lot of negative spacing. More animations tend to negate the principle described if not done with extreme care.