This is more or less true. The new walls system is a double edged sword. It slows down early player zerg rushes so that a super aggressive human player cannot totally steamroll all of the world within the first 100 turns (AI seems to get walls up by about turn 40-50.) However, because walls are so powerful, AI simply cannot handle them if it is against a player who knows what they are doing. So in sum, the current walls (A) slows humans, and (B) stops AI. The devs might think this is a fair tradeoff for the immense AI bonuses on deity or immortal, but for lower difficulties it certainly would make the game a cakewalk. Again though, I don't know how they can weaken walls at this point without throwing off the balance even further unless they just make a modifier that makes humans walls weaker on low difficulty setting.