Because terrain and interriors will be removed = boosts performance default!
turn off shadows and shaders or whatever will be new = a boost to the new boost!
boost + boost = win?
That is saying that shadows and shaders performance with it enable is equal to the default performance NOW, which is nowhere near true.
So, removing terrain - adding a feature 5x as laggy = people who can't loving control that their computer sucks get a stuffload of lag
I honestly don't know how you got that idea.