One must select green dot speed or so, before the thrust "levers" are pulled back to the climb detent at clean-up altitude, i.e. 1500' agl. The brilliant machine will command idle power if not done correctly.
It's got to have a target when you engage it otherwise it doesn't know where to go! It doesn't have to be green dot. All quite sensible really.
Also don't forget, a simple button press puts the levers completely back under your own control (which I think is wherer they should be when manually flying - but that's a totally personal preference).