The AI gets range bonuses on many things, at higher difficulty levels (above normal difficulty).  The devs honestly dont want to put all of these bonuses in here, but until they can really get the AI to properly stand and eventually run on both feet, things like this will be needed to give disparity between the difficulty levels.

I really doubt they have an AI developed system that says "ok, on challenging level, only spend X computations to determine best decision, on tough spend Y computations, on suicidal spend X*Y computations, on easy level, just go full retard".  

Instead of range buffs to the AI, they could just give more bonus techs to the AI, more mass reduction, and let it physically build such as ship - if so, wouldnt it be the same result??