Exactly that. They took ages to update Slaanesh because it is not popular, but when they do it's an incomplete update that it's not gonna entice new players because you are basically playing the same things you were already playing, so it keeps being less popular than the other Chaos gods, so it doesn't get updated, etc...
To me this update reeks of lazyness, and that kinda stings after all the years of Slaanesh neglection