Yes you can do either way, any way, but the reason not to is when you sooner or later go to add other software it will often want to place either folders or files in the root that almost guaranteed will interfere with your forum and you then either need to move the forum or not install this new software.
I'm just trying to help him out with "potential" issues in the future as I've seen it a few times and was a pain to clean it all up.
