@fleschler Your friend is very typical of a number of a'philes who much prefer putting their money into gear than into the room acoustics! Crazy to do this, IME.
The benefit he would get with going to similar lengths as you did to treat his room would far off-set the differences he likely got from lowering the far too high YG tweeters. Windows behind speakers is also never a great thing, IMO. That, plus his room is basically a square results in the sound you describe.