The reason why the "pull trick" is like alt d and why it lumped it in is because it breaks the rules of the game. In aoe3 you have constant stats. Thats just the way the game works. A tc has 6500 hp, a wall has 3000 hp, a musketeer has 150, 23 attack, 4 speed, and 20%(?) resist. Now there are ways you can improve these stats. You tech. Veteran musketeers, advanced buildings, counter infantry rifling all change a units set stats to another set stats. Many civs have unique ways of changing civs stats too with other units, buildings etc. The diamyo boosts units attacks, inspiration boosts units stats etc. Every single way of changing a unit stat has a singular set in stone way of doing it. Move a unit into an aura, send a shipment, click a tech. The "pull trick" changes a constant stat in a way that goes against the rules of the game. First off, its free. Name a singular other way that you can boost a units stats for free. Cover mode maybe, you increase resist but lose speed and attack, so it can hardly be considered overall to be a boost. Second, every single other way of boosting stats has a set way of doing so. You click the veteran upgrade, you send advanced buildings, you have have the ashi close to the diamyo. There is no other stat that is improved "mechanically", so to speak. There is not a singular other way in this game to changes a units stats at will(and for the better) besides pulling.
Its impossible to argue that its not a bug, unless you think the developers intended it to be there. A bug is an error, flaw, failure or fault in a computer program or system that causes it to produce an incorrect or unexpected result, or to behave in unintended ways.If you dont think the "pull trick" causes units to behave in unintended ways I dont even know what more I can say. The fact is it is 1) a bug that 2)breaks rules set by the game.