Hello 3ventic,
well, that is something at least. So bigger Channels would probably need a workaround then…
I will try it with the undocumented call to get the list of Chatters before Join, then hoping for Join/Part events to get fired for huge amount of Join and Leave situations.
A “should be consistent to that end” by a Twitch Staff should be enough to me for the moment to dont give up the whole Project 
Best wishes
Dan