LoadLevelAdditiveAsync useless?

I have 3 scenes setup.

1. Just a simple menu, from which I can choose other scenes. I selected a scene which was loaded via LoadLevel, which was

2. a transition scene only playing 2 animations and showing a text.

3. Is the level to be loaded asynchronously via LoadLevelAdditiveAsync

From Debug logging the loading status I could confirm, that the content was actually loaded async. All good up to here. As soon as the new content loading kicked in the animation I played just froze. Took about 3 seconds, then the animation went on and I could see the scene contents. That's all on mobile. From the profiler (taken off of the editor, and I know the documentation says it's slower, but does show the same behaviour) I got this:

That huge spike is apparently caused by some Loading.AwakeFromLoad. I already tested to disable all Gameobjects with scripts on them, even returned from any Awake() methods instantly, since they are not ignored by simply disabling Gamebjects. I litterally stripped the whole scene from everything that's not a sprite.

What else is needed to get an additive load to smoothly integrate the new content? There seems to be no way to control how fast or on what thread new stuff is loaded? Maybe one needs to parse everything into some XLM document after scene setup and do an instantiate routine by themselves, I don't know.

Would be great if there was a little more about how this is supposed to be addressed, the documentation does not say anything about those Profiler functions, nor how content is loaded in which order or on what thread or... ???

I mean smoothness is kind of the most important part about a good game experience, right?