Maybe your friend found some kind of exploit to level his weapon skill(s) up by doing what you described but generally (at least i think so) IronGate patched the abilitiy to raise your combat skills by attacking inanimate objects (trees, rocks, etc.) out a long while ago.
Maybe it still works if you attack player-build objects that have hitpoints and that can be destroyed (i dont know that as i dont use such exploits).