If I remember previous topics about this correctly, this inefficency was intentionally built into the game to force the player to make strategic decisions about spending, rather than being able to crank out as much as you want at any time.
I'd agree with the argument in principles at least. But the whole point of the actual sliders 'variation' is that there is a mathematic CONSTANT involved. One player can manage two specific areas; Research & Productions (that one being split into Social Manufacturing and/or/nor Shipyard output).
The logic of it is more of a philosophical manner than a true control over any consequences, be it into focus on each planets or applied empire wide.
To me the 100% productivity ---MUST--- be limited somehow to real products since the result will always be the same; elements that come into gameplay and which have certain values as they are tied with a number of strategies. The management part is a different issue as that means more like adapting choices and surface designs than exploiting whatever limits we are given. Brake (or change, even if only to provide a full 300% relative total) that principle, this game becomes something else altogether.
Not only that, the entire mechanics of buildings (cost, maintenance, effects, etc) would also need a complete overhaul to lock up the new balancing factors in such a way that AIs would still be 'smart' enough to compete in many aspects.
And, then there is the BCs calculations; this is also important for a lot of reasons. Morale, Influence & available spending power. Three of many, many more.
The illusion of
lowest effects because of limited sliders is just that - an illusion. Or something to handle, properly.
Etc, Etc!!
