When new videos are added to your Library, there is a slight delay before they're actually added to collections and playlists, this is normal.
In normal use, you wouldn't notice this at all. I think you're a little too focused on trying to see it all happen immediately, when in actual real case usage of the system, that's not really an actual scenario.
While there are still a couple issues with collections and playlists updating, it's for other reasons, which we'll get handled and could possibly even make what you see better, but as for this report, it's working as it should. Things are in fact sorted correctly.