There are two basic points made in the article, which are that difficulty steadily ramps up, and there are changes in AI behavior according to what you do to their plans. So shooting down that scout will discourage them from harvesting and base building, but it will get them looking for yours. The ramping difficulty is there so that things don't get progressively easier as you acquire better ships, weapons, armor, and soldiers. Also means you'll have to move your ass, but it ramps up more slowly in the easier settings, so there'll be an option for everyone. Personally, I like knowing that I've got to kill the aliens before they kill me.